6251 lines
220 KiB
Plaintext
6251 lines
220 KiB
Plaintext
acpi= [HW,ACPI,X86,ARM64]
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Advanced Configuration and Power Interface
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Format: { force | on | off | strict | noirq | rsdt |
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copy_dsdt }
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force -- enable ACPI if default was off
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on -- enable ACPI but allow fallback to DT [arm64]
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off -- disable ACPI if default was on
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noirq -- do not use ACPI for IRQ routing
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strict -- Be less tolerant of platforms that are not
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strictly ACPI specification compliant.
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rsdt -- prefer RSDT over (default) XSDT
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copy_dsdt -- copy DSDT to memory
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For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force"
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are available
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See also Documentation/power/runtime_pm.rst, pci=noacpi
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acpi_apic_instance= [ACPI, IOAPIC]
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Format: <int>
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2: use 2nd APIC table, if available
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1,0: use 1st APIC table
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default: 0
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acpi_backlight= [HW,ACPI]
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{ vendor | video | native | none }
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If set to vendor, prefer vendor-specific driver
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(e.g. thinkpad_acpi, sony_acpi, etc.) instead
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of the ACPI video.ko driver.
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If set to video, use the ACPI video.ko driver.
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If set to native, use the device's native backlight mode.
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If set to none, disable the ACPI backlight interface.
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acpi_force_32bit_fadt_addr
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force FADT to use 32 bit addresses rather than the
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64 bit X_* addresses. Some firmware have broken 64
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bit addresses for force ACPI ignore these and use
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the older legacy 32 bit addresses.
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acpica_no_return_repair [HW, ACPI]
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Disable AML predefined validation mechanism
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This mechanism can repair the evaluation result to make
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the return objects more ACPI specification compliant.
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This option is useful for developers to identify the
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root cause of an AML interpreter issue when the issue
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has something to do with the repair mechanism.
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acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
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acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
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Format: <int>
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CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
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debug output. Bits in debug_layer correspond to a
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_COMPONENT in an ACPI source file, e.g.,
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#define _COMPONENT ACPI_EVENTS
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Bits in debug_level correspond to a level in
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ACPI_DEBUG_PRINT statements, e.g.,
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ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
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The debug_level mask defaults to "info". See
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Documentation/firmware-guide/acpi/debug.rst for more information about
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debug layers and levels.
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Enable processor driver info messages:
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acpi.debug_layer=0x20000000
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Enable AML "Debug" output, i.e., stores to the Debug
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object while interpreting AML:
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acpi.debug_layer=0xffffffff acpi.debug_level=0x2
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Enable all messages related to ACPI hardware:
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acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
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Some values produce so much output that the system is
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unusable. The "log_buf_len" parameter may be useful
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if you need to capture more output.
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acpi_enforce_resources= [ACPI]
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{ strict | lax | no }
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Check for resource conflicts between native drivers
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and ACPI OperationRegions (SystemIO and SystemMemory
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only). IO ports and memory declared in ACPI might be
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used by the ACPI subsystem in arbitrary AML code and
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can interfere with legacy drivers.
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strict (default): access to resources claimed by ACPI
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is denied; legacy drivers trying to access reserved
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resources will fail to bind to device using them.
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lax: access to resources claimed by ACPI is allowed;
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legacy drivers trying to access reserved resources
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will bind successfully but a warning message is logged.
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no: ACPI OperationRegions are not marked as reserved,
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no further checks are performed.
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acpi_force_table_verification [HW,ACPI]
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Enable table checksum verification during early stage.
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By default, this is disabled due to x86 early mapping
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size limitation.
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acpi_irq_balance [HW,ACPI]
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ACPI will balance active IRQs
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default in APIC mode
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acpi_irq_nobalance [HW,ACPI]
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ACPI will not move active IRQs (default)
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default in PIC mode
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acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
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Format: <irq>,<irq>...
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acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
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use by PCI
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Format: <irq>,<irq>...
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acpi_mask_gpe= [HW,ACPI]
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Due to the existence of _Lxx/_Exx, some GPEs triggered
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by unsupported hardware/firmware features can result in
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GPE floodings that cannot be automatically disabled by
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the GPE dispatcher.
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This facility can be used to prevent such uncontrolled
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GPE floodings.
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Format: <byte>
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acpi_no_auto_serialize [HW,ACPI]
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Disable auto-serialization of AML methods
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AML control methods that contain the opcodes to create
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named objects will be marked as "Serialized" by the
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auto-serialization feature.
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This feature is enabled by default.
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This option allows to turn off the feature.
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acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
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kernels.
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acpi_no_static_ssdt [HW,ACPI]
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Disable installation of static SSDTs at early boot time
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By default, SSDTs contained in the RSDT/XSDT will be
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installed automatically and they will appear under
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/sys/firmware/acpi/tables.
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This option turns off this feature.
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Note that specifying this option does not affect
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dynamic table installation which will install SSDT
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tables to /sys/firmware/acpi/tables/dynamic.
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acpi_no_watchdog [HW,ACPI,WDT]
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Ignore the ACPI-based watchdog interface (WDAT) and let
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a native driver control the watchdog device instead.
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acpi_rsdp= [ACPI,EFI,KEXEC]
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Pass the RSDP address to the kernel, mostly used
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on machines running EFI runtime service to boot the
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second kernel for kdump.
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acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
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Format: To spoof as Windows 98: ="Microsoft Windows"
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acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
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of 2 which is mandated by ACPI 6) as the supported ACPI
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specification revision (when using this switch, it may
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be necessary to carry out a cold reboot _twice_ in a
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row to make it take effect on the platform firmware).
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acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
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acpi_osi="string1" # add string1
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acpi_osi="!string2" # remove string2
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acpi_osi=!* # remove all strings
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acpi_osi=! # disable all built-in OS vendor
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strings
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acpi_osi=!! # enable all built-in OS vendor
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strings
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acpi_osi= # disable all strings
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'acpi_osi=!' can be used in combination with single or
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multiple 'acpi_osi="string1"' to support specific OS
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vendor string(s). Note that such command can only
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affect the default state of the OS vendor strings, thus
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it cannot affect the default state of the feature group
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strings and the current state of the OS vendor strings,
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specifying it multiple times through kernel command line
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is meaningless. This command is useful when one do not
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care about the state of the feature group strings which
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should be controlled by the OSPM.
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Examples:
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1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
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to 'acpi_osi="Windows 2000" acpi_osi=!', they all
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can make '_OSI("Windows 2000")' TRUE.
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'acpi_osi=' cannot be used in combination with other
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'acpi_osi=' command lines, the _OSI method will not
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exist in the ACPI namespace. NOTE that such command can
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only affect the _OSI support state, thus specifying it
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multiple times through kernel command line is also
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meaningless.
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Examples:
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1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
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FALSE.
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'acpi_osi=!*' can be used in combination with single or
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multiple 'acpi_osi="string1"' to support specific
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string(s). Note that such command can affect the
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current state of both the OS vendor strings and the
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feature group strings, thus specifying it multiple times
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through kernel command line is meaningful. But it may
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still not able to affect the final state of a string if
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there are quirks related to this string. This command
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is useful when one want to control the state of the
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feature group strings to debug BIOS issues related to
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the OSPM features.
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Examples:
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1. 'acpi_osi="Module Device" acpi_osi=!*' can make
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'_OSI("Module Device")' FALSE.
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2. 'acpi_osi=!* acpi_osi="Module Device"' can make
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'_OSI("Module Device")' TRUE.
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3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
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equivalent to
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'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
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and
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'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
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they all will make '_OSI("Windows 2000")' TRUE.
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acpi_pm_good [X86]
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Override the pmtimer bug detection: force the kernel
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to assume that this machine's pmtimer latches its value
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and always returns good values.
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acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
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Format: { level | edge | high | low }
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acpi_skip_timer_override [HW,ACPI]
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Recognize and ignore IRQ0/pin2 Interrupt Override.
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For broken nForce2 BIOS resulting in XT-PIC timer.
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acpi_sleep= [HW,ACPI] Sleep options
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Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
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old_ordering, nonvs, sci_force_enable, nobl }
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See Documentation/power/video.rst for information on
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s3_bios and s3_mode.
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s3_beep is for debugging; it makes the PC's speaker beep
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as soon as the kernel's real-mode entry point is called.
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s4_nohwsig prevents ACPI hardware signature from being
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used during resume from hibernation.
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old_ordering causes the ACPI 1.0 ordering of the _PTS
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control method, with respect to putting devices into
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low power states, to be enforced (the ACPI 2.0 ordering
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of _PTS is used by default).
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nonvs prevents the kernel from saving/restoring the
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ACPI NVS memory during suspend/hibernation and resume.
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sci_force_enable causes the kernel to set SCI_EN directly
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on resume from S1/S3 (which is against the ACPI spec,
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but some broken systems don't work without it).
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nobl causes the internal blacklist of systems known to
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behave incorrectly in some ways with respect to system
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suspend and resume to be ignored (use wisely).
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acpi_use_timer_override [HW,ACPI]
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Use timer override. For some broken Nvidia NF5 boards
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that require a timer override, but don't have HPET
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add_efi_memmap [EFI; X86] Include EFI memory map in
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kernel's map of available physical RAM.
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agp= [AGP]
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{ off | try_unsupported }
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off: disable AGP support
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try_unsupported: try to drive unsupported chipsets
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(may crash computer or cause data corruption)
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ALSA [HW,ALSA]
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See Documentation/sound/alsa-configuration.rst
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alignment= [KNL,ARM]
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Allow the default userspace alignment fault handler
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behaviour to be specified. Bit 0 enables warnings,
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bit 1 enables fixups, and bit 2 sends a segfault.
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align_va_addr= [X86-64]
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Align virtual addresses by clearing slice [14:12] when
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allocating a VMA at process creation time. This option
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gives you up to 3% performance improvement on AMD F15h
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machines (where it is enabled by default) for a
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CPU-intensive style benchmark, and it can vary highly in
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a microbenchmark depending on workload and compiler.
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32: only for 32-bit processes
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64: only for 64-bit processes
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on: enable for both 32- and 64-bit processes
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off: disable for both 32- and 64-bit processes
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alloc_snapshot [FTRACE]
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Allocate the ftrace snapshot buffer on boot up when the
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main buffer is allocated. This is handy if debugging
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and you need to use tracing_snapshot() on boot up, and
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do not want to use tracing_snapshot_alloc() as it needs
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to be done where GFP_KERNEL allocations are allowed.
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amd_iommu= [HW,X86-64]
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Pass parameters to the AMD IOMMU driver in the system.
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Possible values are:
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fullflush - enable flushing of IO/TLB entries when
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they are unmapped. Otherwise they are
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flushed before they will be reused, which
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is a lot of faster
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off - do not initialize any AMD IOMMU found in
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the system
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force_isolation - Force device isolation for all
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devices. The IOMMU driver is not
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allowed anymore to lift isolation
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requirements as needed. This option
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does not override iommu=pt
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amd_iommu_dump= [HW,X86-64]
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Enable AMD IOMMU driver option to dump the ACPI table
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for AMD IOMMU. With this option enabled, AMD IOMMU
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driver will print ACPI tables for AMD IOMMU during
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IOMMU initialization.
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amd_iommu_intr= [HW,X86-64]
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Specifies one of the following AMD IOMMU interrupt
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remapping modes:
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legacy - Use legacy interrupt remapping mode.
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vapic - Use virtual APIC mode, which allows IOMMU
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to inject interrupts directly into guest.
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This mode requires kvm-amd.avic=1.
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(Default when IOMMU HW support is present.)
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amijoy.map= [HW,JOY] Amiga joystick support
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Map of devices attached to JOY0DAT and JOY1DAT
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Format: <a>,<b>
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See also Documentation/input/joydev/joystick.rst
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analog.map= [HW,JOY] Analog joystick and gamepad support
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Specifies type or capabilities of an analog joystick
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connected to one of 16 gameports
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Format: <type1>,<type2>,..<type16>
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apc= [HW,SPARC]
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Power management functions (SPARCstation-4/5 + deriv.)
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Format: noidle
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Disable APC CPU standby support. SPARCstation-Fox does
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not play well with APC CPU idle - disable it if you have
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APC and your system crashes randomly.
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apic= [APIC,X86] Advanced Programmable Interrupt Controller
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Change the output verbosity while booting
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Format: { quiet (default) | verbose | debug }
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Change the amount of debugging information output
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when initialising the APIC and IO-APIC components.
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For X86-32, this can also be used to specify an APIC
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driver name.
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Format: apic=driver_name
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Examples: apic=bigsmp
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apic_extnmi= [APIC,X86] External NMI delivery setting
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Format: { bsp (default) | all | none }
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bsp: External NMI is delivered only to CPU 0
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all: External NMIs are broadcast to all CPUs as a
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backup of CPU 0
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none: External NMI is masked for all CPUs. This is
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useful so that a dump capture kernel won't be
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shot down by NMI
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autoconf= [IPV6]
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See Documentation/networking/ipv6.rst.
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show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
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Limit apic dumping. The parameter defines the maximal
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number of local apics being dumped. Also it is possible
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to set it to "all" by meaning -- no limit here.
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Format: { 1 (default) | 2 | ... | all }.
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The parameter valid if only apic=debug or
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apic=verbose is specified.
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Example: apic=debug show_lapic=all
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apm= [APM] Advanced Power Management
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See header of arch/x86/kernel/apm_32.c.
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arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
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Format: <io>,<irq>,<nodeID>
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arm64.nobti [ARM64] Unconditionally disable Branch Target
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Identification support
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arm64.nopauth [ARM64] Unconditionally disable Pointer Authentication
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support
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ataflop= [HW,M68k]
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atarimouse= [HW,MOUSE] Atari Mouse
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atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
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EzKey and similar keyboards
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atkbd.reset= [HW] Reset keyboard during initialization
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atkbd.set= [HW] Select keyboard code set
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Format: <int> (2 = AT (default), 3 = PS/2)
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atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
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keyboards
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atkbd.softraw= [HW] Choose between synthetic and real raw mode
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Format: <bool> (0 = real, 1 = synthetic (default))
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atkbd.softrepeat= [HW]
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Use software keyboard repeat
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audit= [KNL] Enable the audit sub-system
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Format: { "0" | "1" | "off" | "on" }
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0 | off - kernel audit is disabled and can not be
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enabled until the next reboot
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unset - kernel audit is initialized but disabled and
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will be fully enabled by the userspace auditd.
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1 | on - kernel audit is initialized and partially
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enabled, storing at most audit_backlog_limit
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messages in RAM until it is fully enabled by the
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userspace auditd.
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Default: unset
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audit_backlog_limit= [KNL] Set the audit queue size limit.
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Format: <int> (must be >=0)
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Default: 64
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bau= [X86_UV] Enable the BAU on SGI UV. The default
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behavior is to disable the BAU (i.e. bau=0).
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Format: { "0" | "1" }
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0 - Disable the BAU.
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1 - Enable the BAU.
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unset - Disable the BAU.
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baycom_epp= [HW,AX25]
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Format: <io>,<mode>
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baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
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Format: <io>,<mode>
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See header of drivers/net/hamradio/baycom_par.c.
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baycom_ser_fdx= [HW,AX25]
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BayCom Serial Port AX.25 Modem (Full Duplex Mode)
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Format: <io>,<irq>,<mode>[,<baud>]
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See header of drivers/net/hamradio/baycom_ser_fdx.c.
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baycom_ser_hdx= [HW,AX25]
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BayCom Serial Port AX.25 Modem (Half Duplex Mode)
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Format: <io>,<irq>,<mode>
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See header of drivers/net/hamradio/baycom_ser_hdx.c.
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blkdevparts= Manual partition parsing of block device(s) for
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embedded devices based on command line input.
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See Documentation/block/cmdline-partition.rst
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boot_delay= Milliseconds to delay each printk during boot.
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Values larger than 10 seconds (10000) are changed to
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no delay (0).
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Format: integer
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bootconfig [KNL]
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Extended command line options can be added to an initrd
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and this will cause the kernel to look for it.
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See Documentation/admin-guide/bootconfig.rst
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bert_disable [ACPI]
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Disable BERT OS support on buggy BIOSes.
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bgrt_disable [ACPI][X86]
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Disable BGRT to avoid flickering OEM logo.
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bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
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bttv.radio= Most important insmod options are available as
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kernel args too.
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bttv.pll= See Documentation/admin-guide/media/bttv.rst
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bttv.tuner=
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bulk_remove=off [PPC] This parameter disables the use of the pSeries
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firmware feature for flushing multiple hpte entries
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at a time.
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|
|
c101= [NET] Moxa C101 synchronous serial card
|
|
|
|
cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
|
|
Sometimes CPU hardware bugs make them report the cache
|
|
size incorrectly. The kernel will attempt work arounds
|
|
to fix known problems, but for some CPUs it is not
|
|
possible to determine what the correct size should be.
|
|
This option provides an override for these situations.
|
|
|
|
carrier_timeout=
|
|
[NET] Specifies amount of time (in seconds) that
|
|
the kernel should wait for a network carrier. By default
|
|
it waits 120 seconds.
|
|
|
|
ca_keys= [KEYS] This parameter identifies a specific key(s) on
|
|
the system trusted keyring to be used for certificate
|
|
trust validation.
|
|
format: { id:<keyid> | builtin }
|
|
|
|
cca= [MIPS] Override the kernel pages' cache coherency
|
|
algorithm. Accepted values range from 0 to 7
|
|
inclusive. See arch/mips/include/asm/pgtable-bits.h
|
|
for platform specific values (SB1, Loongson3 and
|
|
others).
|
|
|
|
ccw_timeout_log [S390]
|
|
See Documentation/s390/common_io.rst for details.
|
|
|
|
cgroup_disable= [KNL] Disable a particular controller
|
|
Format: {name of the controller(s) to disable}
|
|
The effects of cgroup_disable=foo are:
|
|
- foo isn't auto-mounted if you mount all cgroups in
|
|
a single hierarchy
|
|
- foo isn't visible as an individually mountable
|
|
subsystem
|
|
{Currently only "memory" controller deal with this and
|
|
cut the overhead, others just disable the usage. So
|
|
only cgroup_disable=memory is actually worthy}
|
|
|
|
cgroup_no_v1= [KNL] Disable cgroup controllers and named hierarchies in v1
|
|
Format: { { controller | "all" | "named" }
|
|
[,{ controller | "all" | "named" }...] }
|
|
Like cgroup_disable, but only applies to cgroup v1;
|
|
the blacklisted controllers remain available in cgroup2.
|
|
"all" blacklists all controllers and "named" disables
|
|
named mounts. Specifying both "all" and "named" disables
|
|
all v1 hierarchies.
|
|
|
|
cgroup.memory= [KNL] Pass options to the cgroup memory controller.
|
|
Format: <string>
|
|
nosocket -- Disable socket memory accounting.
|
|
nokmem -- Disable kernel memory accounting.
|
|
|
|
checkreqprot [SELINUX] Set initial checkreqprot flag value.
|
|
Format: { "0" | "1" }
|
|
See security/selinux/Kconfig help text.
|
|
0 -- check protection applied by kernel (includes
|
|
any implied execute protection).
|
|
1 -- check protection requested by application.
|
|
Default value is set via a kernel config option.
|
|
Value can be changed at runtime via
|
|
/sys/fs/selinux/checkreqprot.
|
|
Setting checkreqprot to 1 is deprecated.
|
|
|
|
cio_ignore= [S390]
|
|
See Documentation/s390/common_io.rst for details.
|
|
clk_ignore_unused
|
|
[CLK]
|
|
Prevents the clock framework from automatically gating
|
|
clocks that have not been explicitly enabled by a Linux
|
|
device driver but are enabled in hardware at reset or
|
|
by the bootloader/firmware. Note that this does not
|
|
force such clocks to be always-on nor does it reserve
|
|
those clocks in any way. This parameter is useful for
|
|
debug and development, but should not be needed on a
|
|
platform with proper driver support. For more
|
|
information, see Documentation/driver-api/clk.rst.
|
|
|
|
clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
|
|
[Deprecated]
|
|
Forces specified clocksource (if available) to be used
|
|
when calculating gettimeofday(). If specified
|
|
clocksource is not available, it defaults to PIT.
|
|
Format: { pit | tsc | cyclone | pmtmr }
|
|
|
|
clocksource= Override the default clocksource
|
|
Format: <string>
|
|
Override the default clocksource and use the clocksource
|
|
with the name specified.
|
|
Some clocksource names to choose from, depending on
|
|
the platform:
|
|
[all] jiffies (this is the base, fallback clocksource)
|
|
[ACPI] acpi_pm
|
|
[ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
|
|
pxa_timer,timer3,32k_counter,timer0_1
|
|
[X86-32] pit,hpet,tsc;
|
|
scx200_hrt on Geode; cyclone on IBM x440
|
|
[MIPS] MIPS
|
|
[PARISC] cr16
|
|
[S390] tod
|
|
[SH] SuperH
|
|
[SPARC64] tick
|
|
[X86-64] hpet,tsc
|
|
|
|
clocksource.arm_arch_timer.evtstrm=
|
|
[ARM,ARM64]
|
|
Format: <bool>
|
|
Enable/disable the eventstream feature of the ARM
|
|
architected timer so that code using WFE-based polling
|
|
loops can be debugged more effectively on production
|
|
systems.
|
|
|
|
clearcpuid=BITNUM[,BITNUM...] [X86]
|
|
Disable CPUID feature X for the kernel. See
|
|
arch/x86/include/asm/cpufeatures.h for the valid bit
|
|
numbers. Note the Linux specific bits are not necessarily
|
|
stable over kernel options, but the vendor specific
|
|
ones should be.
|
|
Also note that user programs calling CPUID directly
|
|
or using the feature without checking anything
|
|
will still see it. This just prevents it from
|
|
being used by the kernel or shown in /proc/cpuinfo.
|
|
Also note the kernel might malfunction if you disable
|
|
some critical bits.
|
|
|
|
cma=nn[MG]@[start[MG][-end[MG]]]
|
|
[KNL,CMA]
|
|
Sets the size of kernel global memory area for
|
|
contiguous memory allocations and optionally the
|
|
placement constraint by the physical address range of
|
|
memory allocations. A value of 0 disables CMA
|
|
altogether. For more information, see
|
|
kernel/dma/contiguous.c
|
|
|
|
cma_pernuma=nn[MG]
|
|
[ARM64,KNL,CMA]
|
|
Sets the size of kernel per-numa memory area for
|
|
contiguous memory allocations. A value of 0 disables
|
|
per-numa CMA altogether. And If this option is not
|
|
specificed, the default value is 0.
|
|
With per-numa CMA enabled, DMA users on node nid will
|
|
first try to allocate buffer from the pernuma area
|
|
which is located in node nid, if the allocation fails,
|
|
they will fallback to the global default memory area.
|
|
|
|
cmo_free_hint= [PPC] Format: { yes | no }
|
|
Specify whether pages are marked as being inactive
|
|
when they are freed. This is used in CMO environments
|
|
to determine OS memory pressure for page stealing by
|
|
a hypervisor.
|
|
Default: yes
|
|
|
|
coherent_pool=nn[KMG] [ARM,KNL]
|
|
Sets the size of memory pool for coherent, atomic dma
|
|
allocations, by default set to 256K.
|
|
|
|
com20020= [HW,NET] ARCnet - COM20020 chipset
|
|
Format:
|
|
<io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
|
|
|
|
com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
|
|
Format: <io>[,<irq>]
|
|
|
|
com90xx= [HW,NET]
|
|
ARCnet - COM90xx chipset (memory-mapped buffers)
|
|
Format: <io>[,<irq>[,<memstart>]]
|
|
|
|
condev= [HW,S390] console device
|
|
conmode=
|
|
|
|
console= [KNL] Output console device and options.
|
|
|
|
tty<n> Use the virtual console device <n>.
|
|
|
|
ttyS<n>[,options]
|
|
ttyUSB0[,options]
|
|
Use the specified serial port. The options are of
|
|
the form "bbbbpnf", where "bbbb" is the baud rate,
|
|
"p" is parity ("n", "o", or "e"), "n" is number of
|
|
bits, and "f" is flow control ("r" for RTS or
|
|
omit it). Default is "9600n8".
|
|
|
|
See Documentation/admin-guide/serial-console.rst for more
|
|
information. See
|
|
Documentation/networking/netconsole.rst for an
|
|
alternative.
|
|
|
|
uart[8250],io,<addr>[,options]
|
|
uart[8250],mmio,<addr>[,options]
|
|
uart[8250],mmio16,<addr>[,options]
|
|
uart[8250],mmio32,<addr>[,options]
|
|
uart[8250],0x<addr>[,options]
|
|
Start an early, polled-mode console on the 8250/16550
|
|
UART at the specified I/O port or MMIO address,
|
|
switching to the matching ttyS device later.
|
|
MMIO inter-register address stride is either 8-bit
|
|
(mmio), 16-bit (mmio16), or 32-bit (mmio32).
|
|
If none of [io|mmio|mmio16|mmio32], <addr> is assumed
|
|
to be equivalent to 'mmio'. 'options' are specified in
|
|
the same format described for ttyS above; if unspecified,
|
|
the h/w is not re-initialized.
|
|
|
|
hvc<n> Use the hypervisor console device <n>. This is for
|
|
both Xen and PowerPC hypervisors.
|
|
|
|
If the device connected to the port is not a TTY but a braille
|
|
device, prepend "brl," before the device type, for instance
|
|
console=brl,ttyS0
|
|
For now, only VisioBraille is supported.
|
|
|
|
console_msg_format=
|
|
[KNL] Change console messages format
|
|
default
|
|
By default we print messages on consoles in
|
|
"[time stamp] text\n" format (time stamp may not be
|
|
printed, depending on CONFIG_PRINTK_TIME or
|
|
`printk_time' param).
|
|
syslog
|
|
Switch to syslog format: "<%u>[time stamp] text\n"
|
|
IOW, each message will have a facility and loglevel
|
|
prefix. The format is similar to one used by syslog()
|
|
syscall, or to executing "dmesg -S --raw" or to reading
|
|
from /proc/kmsg.
|
|
|
|
consoleblank= [KNL] The console blank (screen saver) timeout in
|
|
seconds. A value of 0 disables the blank timer.
|
|
Defaults to 0.
|
|
|
|
coredump_filter=
|
|
[KNL] Change the default value for
|
|
/proc/<pid>/coredump_filter.
|
|
See also Documentation/filesystems/proc.rst.
|
|
|
|
coresight_cpu_debug.enable
|
|
[ARM,ARM64]
|
|
Format: <bool>
|
|
Enable/disable the CPU sampling based debugging.
|
|
0: default value, disable debugging
|
|
1: enable debugging at boot time
|
|
|
|
cpuidle.off=1 [CPU_IDLE]
|
|
disable the cpuidle sub-system
|
|
|
|
cpuidle.governor=
|
|
[CPU_IDLE] Name of the cpuidle governor to use.
|
|
|
|
cpufreq.off=1 [CPU_FREQ]
|
|
disable the cpufreq sub-system
|
|
|
|
cpufreq.default_governor=
|
|
[CPU_FREQ] Name of the default cpufreq governor or
|
|
policy to use. This governor must be registered in the
|
|
kernel before the cpufreq driver probes.
|
|
|
|
cpu_init_udelay=N
|
|
[X86] Delay for N microsec between assert and de-assert
|
|
of APIC INIT to start processors. This delay occurs
|
|
on every CPU online, such as boot, and resume from suspend.
|
|
Default: 10000
|
|
|
|
cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
|
|
Format:
|
|
<first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
|
|
|
|
crashkernel=size[KMG][@offset[KMG]]
|
|
[KNL] Using kexec, Linux can switch to a 'crash kernel'
|
|
upon panic. This parameter reserves the physical
|
|
memory region [offset, offset + size] for that kernel
|
|
image. If '@offset' is omitted, then a suitable offset
|
|
is selected automatically.
|
|
[KNL, X86-64] Select a region under 4G first, and
|
|
fall back to reserve region above 4G when '@offset'
|
|
hasn't been specified.
|
|
See Documentation/admin-guide/kdump/kdump.rst for further details.
|
|
|
|
crashkernel=range1:size1[,range2:size2,...][@offset]
|
|
[KNL] Same as above, but depends on the memory
|
|
in the running system. The syntax of range is
|
|
start-[end] where start and end are both
|
|
a memory unit (amount[KMG]). See also
|
|
Documentation/admin-guide/kdump/kdump.rst for an example.
|
|
|
|
crashkernel=size[KMG],high
|
|
[KNL, X86-64] range could be above 4G. Allow kernel
|
|
to allocate physical memory region from top, so could
|
|
be above 4G if system have more than 4G ram installed.
|
|
Otherwise memory region will be allocated below 4G, if
|
|
available.
|
|
It will be ignored if crashkernel=X is specified.
|
|
crashkernel=size[KMG],low
|
|
[KNL, X86-64] range under 4G. When crashkernel=X,high
|
|
is passed, kernel could allocate physical memory region
|
|
above 4G, that cause second kernel crash on system
|
|
that require some amount of low memory, e.g. swiotlb
|
|
requires at least 64M+32K low memory, also enough extra
|
|
low memory is needed to make sure DMA buffers for 32-bit
|
|
devices won't run out. Kernel would try to allocate at
|
|
at least 256M below 4G automatically.
|
|
This one let user to specify own low range under 4G
|
|
for second kernel instead.
|
|
0: to disable low allocation.
|
|
It will be ignored when crashkernel=X,high is not used
|
|
or memory reserved is below 4G.
|
|
|
|
cryptomgr.notests
|
|
[KNL] Disable crypto self-tests
|
|
|
|
cs89x0_dma= [HW,NET]
|
|
Format: <dma>
|
|
|
|
cs89x0_media= [HW,NET]
|
|
Format: { rj45 | aui | bnc }
|
|
|
|
csdlock_debug= [KNL] Enable debug add-ons of cross-CPU function call
|
|
handling. When switched on, additional debug data is
|
|
printed to the console in case a hanging CPU is
|
|
detected, and that CPU is pinged again in order to try
|
|
to resolve the hang situation.
|
|
0: disable csdlock debugging (default)
|
|
1: enable basic csdlock debugging (minor impact)
|
|
ext: enable extended csdlock debugging (more impact,
|
|
but more data)
|
|
|
|
dasd= [HW,NET]
|
|
See header of drivers/s390/block/dasd_devmap.c.
|
|
|
|
db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
|
|
(one device per port)
|
|
Format: <port#>,<type>
|
|
See also Documentation/input/devices/joystick-parport.rst
|
|
|
|
ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
|
|
time. See
|
|
Documentation/admin-guide/dynamic-debug-howto.rst for
|
|
details. Deprecated, see dyndbg.
|
|
|
|
debug [KNL] Enable kernel debugging (events log level).
|
|
|
|
debug_boot_weak_hash
|
|
[KNL] Enable printing [hashed] pointers early in the
|
|
boot sequence. If enabled, we use a weak hash instead
|
|
of siphash to hash pointers. Use this option if you are
|
|
seeing instances of '(___ptrval___)') and need to see a
|
|
value (hashed pointer) instead. Cryptographically
|
|
insecure, please do not use on production kernels.
|
|
|
|
debug_locks_verbose=
|
|
[KNL] verbose locking self-tests
|
|
Format: <int>
|
|
Print debugging info while doing the locking API
|
|
self-tests.
|
|
Bitmask for the various LOCKTYPE_ tests. Defaults to 0
|
|
(no extra messages), setting it to -1 (all bits set)
|
|
will print _a_lot_ more information - normally only
|
|
useful to lockdep developers.
|
|
|
|
debug_objects [KNL] Enable object debugging
|
|
|
|
no_debug_objects
|
|
[KNL] Disable object debugging
|
|
|
|
debug_guardpage_minorder=
|
|
[KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
|
|
parameter allows control of the order of pages that will
|
|
be intentionally kept free (and hence protected) by the
|
|
buddy allocator. Bigger value increase the probability
|
|
of catching random memory corruption, but reduce the
|
|
amount of memory for normal system use. The maximum
|
|
possible value is MAX_ORDER/2. Setting this parameter
|
|
to 1 or 2 should be enough to identify most random
|
|
memory corruption problems caused by bugs in kernel or
|
|
driver code when a CPU writes to (or reads from) a
|
|
random memory location. Note that there exists a class
|
|
of memory corruptions problems caused by buggy H/W or
|
|
F/W or by drivers badly programing DMA (basically when
|
|
memory is written at bus level and the CPU MMU is
|
|
bypassed) which are not detectable by
|
|
CONFIG_DEBUG_PAGEALLOC, hence this option will not help
|
|
tracking down these problems.
|
|
|
|
debug_pagealloc=
|
|
[KNL] When CONFIG_DEBUG_PAGEALLOC is set, this parameter
|
|
enables the feature at boot time. By default, it is
|
|
disabled and the system will work mostly the same as a
|
|
kernel built without CONFIG_DEBUG_PAGEALLOC.
|
|
Note: to get most of debug_pagealloc error reports, it's
|
|
useful to also enable the page_owner functionality.
|
|
on: enable the feature
|
|
|
|
debugfs= [KNL] This parameter enables what is exposed to userspace
|
|
and debugfs internal clients.
|
|
Format: { on, no-mount, off }
|
|
on: All functions are enabled.
|
|
no-mount:
|
|
Filesystem is not registered but kernel clients can
|
|
access APIs and a crashkernel can be used to read
|
|
its content. There is nothing to mount.
|
|
off: Filesystem is not registered and clients
|
|
get a -EPERM as result when trying to register files
|
|
or directories within debugfs.
|
|
This is equivalent of the runtime functionality if
|
|
debugfs was not enabled in the kernel at all.
|
|
Default value is set in build-time with a kernel configuration.
|
|
|
|
debugpat [X86] Enable PAT debugging
|
|
|
|
decnet.addr= [HW,NET]
|
|
Format: <area>[,<node>]
|
|
See also Documentation/networking/decnet.rst.
|
|
|
|
default_hugepagesz=
|
|
[HW] The size of the default HugeTLB page. This is
|
|
the size represented by the legacy /proc/ hugepages
|
|
APIs. In addition, this is the default hugetlb size
|
|
used for shmget(), mmap() and mounting hugetlbfs
|
|
filesystems. If not specified, defaults to the
|
|
architecture's default huge page size. Huge page
|
|
sizes are architecture dependent. See also
|
|
Documentation/admin-guide/mm/hugetlbpage.rst.
|
|
Format: size[KMG]
|
|
|
|
deferred_probe_timeout=
|
|
[KNL] Debugging option to set a timeout in seconds for
|
|
deferred probe to give up waiting on dependencies to
|
|
probe. Only specific dependencies (subsystems or
|
|
drivers) that have opted in will be ignored. A timeout of 0
|
|
will timeout at the end of initcalls. This option will also
|
|
dump out devices still on the deferred probe list after
|
|
retrying.
|
|
|
|
dfltcc= [HW,S390]
|
|
Format: { on | off | def_only | inf_only | always }
|
|
on: s390 zlib hardware support for compression on
|
|
level 1 and decompression (default)
|
|
off: No s390 zlib hardware support
|
|
def_only: s390 zlib hardware support for deflate
|
|
only (compression on level 1)
|
|
inf_only: s390 zlib hardware support for inflate
|
|
only (decompression)
|
|
always: Same as 'on' but ignores the selected compression
|
|
level always using hardware support (used for debugging)
|
|
|
|
dhash_entries= [KNL]
|
|
Set number of hash buckets for dentry cache.
|
|
|
|
disable_1tb_segments [PPC]
|
|
Disables the use of 1TB hash page table segments. This
|
|
causes the kernel to fall back to 256MB segments which
|
|
can be useful when debugging issues that require an SLB
|
|
miss to occur.
|
|
|
|
stress_slb [PPC]
|
|
Limits the number of kernel SLB entries, and flushes
|
|
them frequently to increase the rate of SLB faults
|
|
on kernel addresses.
|
|
|
|
disable= [IPV6]
|
|
See Documentation/networking/ipv6.rst.
|
|
|
|
hardened_usercopy=
|
|
[KNL] Under CONFIG_HARDENED_USERCOPY, whether
|
|
hardening is enabled for this boot. Hardened
|
|
usercopy checking is used to protect the kernel
|
|
from reading or writing beyond known memory
|
|
allocation boundaries as a proactive defense
|
|
against bounds-checking flaws in the kernel's
|
|
copy_to_user()/copy_from_user() interface.
|
|
on Perform hardened usercopy checks (default).
|
|
off Disable hardened usercopy checks.
|
|
|
|
disable_radix [PPC]
|
|
Disable RADIX MMU mode on POWER9
|
|
|
|
radix_hcall_invalidate=on [PPC/PSERIES]
|
|
Disable RADIX GTSE feature and use hcall for TLB
|
|
invalidate.
|
|
|
|
disable_tlbie [PPC]
|
|
Disable TLBIE instruction. Currently does not work
|
|
with KVM, with HASH MMU, or with coherent accelerators.
|
|
|
|
disable_cpu_apicid= [X86,APIC,SMP]
|
|
Format: <int>
|
|
The number of initial APIC ID for the
|
|
corresponding CPU to be disabled at boot,
|
|
mostly used for the kdump 2nd kernel to
|
|
disable BSP to wake up multiple CPUs without
|
|
causing system reset or hang due to sending
|
|
INIT from AP to BSP.
|
|
|
|
disable_ddw [PPC/PSERIES]
|
|
Disable Dynamic DMA Window support. Use this
|
|
to workaround buggy firmware.
|
|
|
|
disable_ipv6= [IPV6]
|
|
See Documentation/networking/ipv6.rst.
|
|
|
|
disable_mtrr_cleanup [X86]
|
|
The kernel tries to adjust MTRR layout from continuous
|
|
to discrete, to make X server driver able to add WB
|
|
entry later. This parameter disables that.
|
|
|
|
disable_mtrr_trim [X86, Intel and AMD only]
|
|
By default the kernel will trim any uncacheable
|
|
memory out of your available memory pool based on
|
|
MTRR settings. This parameter disables that behavior,
|
|
possibly causing your machine to run very slowly.
|
|
|
|
disable_timer_pin_1 [X86]
|
|
Disable PIN 1 of APIC timer
|
|
Can be useful to work around chipset bugs.
|
|
|
|
dis_ucode_ldr [X86] Disable the microcode loader.
|
|
|
|
dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
|
|
this option disables the debugging code at boot.
|
|
|
|
dma_debug_entries=<number>
|
|
This option allows to tune the number of preallocated
|
|
entries for DMA-API debugging code. One entry is
|
|
required per DMA-API allocation. Use this if the
|
|
DMA-API debugging code disables itself because the
|
|
architectural default is too low.
|
|
|
|
dma_debug_driver=<driver_name>
|
|
With this option the DMA-API debugging driver
|
|
filter feature can be enabled at boot time. Just
|
|
pass the driver to filter for as the parameter.
|
|
The filter can be disabled or changed to another
|
|
driver later using sysfs.
|
|
|
|
driver_async_probe= [KNL]
|
|
List of driver names to be probed asynchronously.
|
|
Format: <driver_name1>,<driver_name2>...
|
|
|
|
drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
|
|
Broken monitors, graphic adapters, KVMs and EDIDless
|
|
panels may send no or incorrect EDID data sets.
|
|
This parameter allows to specify an EDID data sets
|
|
in the /lib/firmware directory that are used instead.
|
|
Generic built-in EDID data sets are used, if one of
|
|
edid/1024x768.bin, edid/1280x1024.bin,
|
|
edid/1680x1050.bin, or edid/1920x1080.bin is given
|
|
and no file with the same name exists. Details and
|
|
instructions how to build your own EDID data are
|
|
available in Documentation/admin-guide/edid.rst. An EDID
|
|
data set will only be used for a particular connector,
|
|
if its name and a colon are prepended to the EDID
|
|
name. Each connector may use a unique EDID data
|
|
set by separating the files with a comma. An EDID
|
|
data set with no connector name will be used for
|
|
any connectors not explicitly specified.
|
|
|
|
dscc4.setup= [NET]
|
|
|
|
dt_cpu_ftrs= [PPC]
|
|
Format: {"off" | "known"}
|
|
Control how the dt_cpu_ftrs device-tree binding is
|
|
used for CPU feature discovery and setup (if it
|
|
exists).
|
|
off: Do not use it, fall back to legacy cpu table.
|
|
known: Do not pass through unknown features to guests
|
|
or userspace, only those that the kernel is aware of.
|
|
|
|
dump_apple_properties [X86]
|
|
Dump name and content of EFI device properties on
|
|
x86 Macs. Useful for driver authors to determine
|
|
what data is available or for reverse-engineering.
|
|
|
|
dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
|
|
<module>.dyndbg[="val"]
|
|
Enable debug messages at boot time. See
|
|
Documentation/admin-guide/dynamic-debug-howto.rst
|
|
for details.
|
|
|
|
nopku [X86] Disable Memory Protection Keys CPU feature found
|
|
in some Intel CPUs.
|
|
|
|
<module>.async_probe [KNL]
|
|
Enable asynchronous probe on this module.
|
|
|
|
early_ioremap_debug [KNL]
|
|
Enable debug messages in early_ioremap support. This
|
|
is useful for tracking down temporary early mappings
|
|
which are not unmapped.
|
|
|
|
earlycon= [KNL] Output early console device and options.
|
|
|
|
When used with no options, the early console is
|
|
determined by stdout-path property in device tree's
|
|
chosen node or the ACPI SPCR table if supported by
|
|
the platform.
|
|
|
|
cdns,<addr>[,options]
|
|
Start an early, polled-mode console on a Cadence
|
|
(xuartps) serial port at the specified address. Only
|
|
supported option is baud rate. If baud rate is not
|
|
specified, the serial port must already be setup and
|
|
configured.
|
|
|
|
uart[8250],io,<addr>[,options]
|
|
uart[8250],mmio,<addr>[,options]
|
|
uart[8250],mmio32,<addr>[,options]
|
|
uart[8250],mmio32be,<addr>[,options]
|
|
uart[8250],0x<addr>[,options]
|
|
Start an early, polled-mode console on the 8250/16550
|
|
UART at the specified I/O port or MMIO address.
|
|
MMIO inter-register address stride is either 8-bit
|
|
(mmio) or 32-bit (mmio32 or mmio32be).
|
|
If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
|
|
to be equivalent to 'mmio'. 'options' are specified
|
|
in the same format described for "console=ttyS<n>"; if
|
|
unspecified, the h/w is not initialized.
|
|
|
|
pl011,<addr>
|
|
pl011,mmio32,<addr>
|
|
Start an early, polled-mode console on a pl011 serial
|
|
port at the specified address. The pl011 serial port
|
|
must already be setup and configured. Options are not
|
|
yet supported. If 'mmio32' is specified, then only
|
|
the driver will use only 32-bit accessors to read/write
|
|
the device registers.
|
|
|
|
meson,<addr>
|
|
Start an early, polled-mode console on a meson serial
|
|
port at the specified address. The serial port must
|
|
already be setup and configured. Options are not yet
|
|
supported.
|
|
|
|
msm_serial,<addr>
|
|
Start an early, polled-mode console on an msm serial
|
|
port at the specified address. The serial port
|
|
must already be setup and configured. Options are not
|
|
yet supported.
|
|
|
|
msm_serial_dm,<addr>
|
|
Start an early, polled-mode console on an msm serial
|
|
dm port at the specified address. The serial port
|
|
must already be setup and configured. Options are not
|
|
yet supported.
|
|
|
|
owl,<addr>
|
|
Start an early, polled-mode console on a serial port
|
|
of an Actions Semi SoC, such as S500 or S900, at the
|
|
specified address. The serial port must already be
|
|
setup and configured. Options are not yet supported.
|
|
|
|
rda,<addr>
|
|
Start an early, polled-mode console on a serial port
|
|
of an RDA Micro SoC, such as RDA8810PL, at the
|
|
specified address. The serial port must already be
|
|
setup and configured. Options are not yet supported.
|
|
|
|
sbi
|
|
Use RISC-V SBI (Supervisor Binary Interface) for early
|
|
console.
|
|
|
|
smh Use ARM semihosting calls for early console.
|
|
|
|
s3c2410,<addr>
|
|
s3c2412,<addr>
|
|
s3c2440,<addr>
|
|
s3c6400,<addr>
|
|
s5pv210,<addr>
|
|
exynos4210,<addr>
|
|
Use early console provided by serial driver available
|
|
on Samsung SoCs, requires selecting proper type and
|
|
a correct base address of the selected UART port. The
|
|
serial port must already be setup and configured.
|
|
Options are not yet supported.
|
|
|
|
lantiq,<addr>
|
|
Start an early, polled-mode console on a lantiq serial
|
|
(lqasc) port at the specified address. The serial port
|
|
must already be setup and configured. Options are not
|
|
yet supported.
|
|
|
|
lpuart,<addr>
|
|
lpuart32,<addr>
|
|
Use early console provided by Freescale LP UART driver
|
|
found on Freescale Vybrid and QorIQ LS1021A processors.
|
|
A valid base address must be provided, and the serial
|
|
port must already be setup and configured.
|
|
|
|
ec_imx21,<addr>
|
|
ec_imx6q,<addr>
|
|
Start an early, polled-mode, output-only console on the
|
|
Freescale i.MX UART at the specified address. The UART
|
|
must already be setup and configured.
|
|
|
|
ar3700_uart,<addr>
|
|
Start an early, polled-mode console on the
|
|
Armada 3700 serial port at the specified
|
|
address. The serial port must already be setup
|
|
and configured. Options are not yet supported.
|
|
|
|
qcom_geni,<addr>
|
|
Start an early, polled-mode console on a Qualcomm
|
|
Generic Interface (GENI) based serial port at the
|
|
specified address. The serial port must already be
|
|
setup and configured. Options are not yet supported.
|
|
|
|
efifb,[options]
|
|
Start an early, unaccelerated console on the EFI
|
|
memory mapped framebuffer (if available). On cache
|
|
coherent non-x86 systems that use system memory for
|
|
the framebuffer, pass the 'ram' option so that it is
|
|
mapped with the correct attributes.
|
|
|
|
linflex,<addr>
|
|
Use early console provided by Freescale LINFlexD UART
|
|
serial driver for NXP S32V234 SoCs. A valid base
|
|
address must be provided, and the serial port must
|
|
already be setup and configured.
|
|
|
|
earlyprintk= [X86,SH,ARM,M68k,S390]
|
|
earlyprintk=vga
|
|
earlyprintk=sclp
|
|
earlyprintk=xen
|
|
earlyprintk=serial[,ttySn[,baudrate]]
|
|
earlyprintk=serial[,0x...[,baudrate]]
|
|
earlyprintk=ttySn[,baudrate]
|
|
earlyprintk=dbgp[debugController#]
|
|
earlyprintk=pciserial[,force],bus:device.function[,baudrate]
|
|
earlyprintk=xdbc[xhciController#]
|
|
|
|
earlyprintk is useful when the kernel crashes before
|
|
the normal console is initialized. It is not enabled by
|
|
default because it has some cosmetic problems.
|
|
|
|
Append ",keep" to not disable it when the real console
|
|
takes over.
|
|
|
|
Only one of vga, efi, serial, or usb debug port can
|
|
be used at a time.
|
|
|
|
Currently only ttyS0 and ttyS1 may be specified by
|
|
name. Other I/O ports may be explicitly specified
|
|
on some architectures (x86 and arm at least) by
|
|
replacing ttySn with an I/O port address, like this:
|
|
earlyprintk=serial,0x1008,115200
|
|
You can find the port for a given device in
|
|
/proc/tty/driver/serial:
|
|
2: uart:ST16650V2 port:00001008 irq:18 ...
|
|
|
|
Interaction with the standard serial driver is not
|
|
very good.
|
|
|
|
The VGA and EFI output is eventually overwritten by
|
|
the real console.
|
|
|
|
The xen output can only be used by Xen PV guests.
|
|
|
|
The sclp output can only be used on s390.
|
|
|
|
The optional "force" to "pciserial" enables use of a
|
|
PCI device even when its classcode is not of the
|
|
UART class.
|
|
|
|
edac_report= [HW,EDAC] Control how to report EDAC event
|
|
Format: {"on" | "off" | "force"}
|
|
on: enable EDAC to report H/W event. May be overridden
|
|
by other higher priority error reporting module.
|
|
off: disable H/W event reporting through EDAC.
|
|
force: enforce the use of EDAC to report H/W event.
|
|
default: on.
|
|
|
|
ekgdboc= [X86,KGDB] Allow early kernel console debugging
|
|
ekgdboc=kbd
|
|
|
|
This is designed to be used in conjunction with
|
|
the boot argument: earlyprintk=vga
|
|
|
|
This parameter works in place of the kgdboc parameter
|
|
but can only be used if the backing tty is available
|
|
very early in the boot process. For early debugging
|
|
via a serial port see kgdboc_earlycon instead.
|
|
|
|
edd= [EDD]
|
|
Format: {"off" | "on" | "skip[mbr]"}
|
|
|
|
efi= [EFI]
|
|
Format: { "debug", "disable_early_pci_dma",
|
|
"nochunk", "noruntime", "nosoftreserve",
|
|
"novamap", "no_disable_early_pci_dma" }
|
|
debug: enable misc debug output.
|
|
disable_early_pci_dma: disable the busmaster bit on all
|
|
PCI bridges while in the EFI boot stub.
|
|
nochunk: disable reading files in "chunks" in the EFI
|
|
boot stub, as chunking can cause problems with some
|
|
firmware implementations.
|
|
noruntime : disable EFI runtime services support
|
|
nosoftreserve: The EFI_MEMORY_SP (Specific Purpose)
|
|
attribute may cause the kernel to reserve the
|
|
memory range for a memory mapping driver to
|
|
claim. Specify efi=nosoftreserve to disable this
|
|
reservation and treat the memory by its base type
|
|
(i.e. EFI_CONVENTIONAL_MEMORY / "System RAM").
|
|
novamap: do not call SetVirtualAddressMap().
|
|
no_disable_early_pci_dma: Leave the busmaster bit set
|
|
on all PCI bridges while in the EFI boot stub
|
|
|
|
efi_no_storage_paranoia [EFI; X86]
|
|
Using this parameter you can use more than 50% of
|
|
your efi variable storage. Use this parameter only if
|
|
you are really sure that your UEFI does sane gc and
|
|
fulfills the spec otherwise your board may brick.
|
|
|
|
efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
|
|
Add arbitrary attribute to specific memory range by
|
|
updating original EFI memory map.
|
|
Region of memory which aa attribute is added to is
|
|
from ss to ss+nn.
|
|
|
|
If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
|
|
is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
|
|
attribute is added to range 0x100000000-0x180000000 and
|
|
0x10a0000000-0x1120000000.
|
|
|
|
If efi_fake_mem=8G@9G:0x40000 is specified, the
|
|
EFI_MEMORY_SP(0x40000) attribute is added to
|
|
range 0x240000000-0x43fffffff.
|
|
|
|
Using this parameter you can do debugging of EFI memmap
|
|
related features. For example, you can do debugging of
|
|
Address Range Mirroring feature even if your box
|
|
doesn't support it, or mark specific memory as
|
|
"soft reserved".
|
|
|
|
efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
|
|
that is to be dynamically loaded by Linux. If there are
|
|
multiple variables with the same name but with different
|
|
vendor GUIDs, all of them will be loaded. See
|
|
Documentation/admin-guide/acpi/ssdt-overlays.rst for details.
|
|
|
|
|
|
eisa_irq_edge= [PARISC,HW]
|
|
See header of drivers/parisc/eisa.c.
|
|
|
|
elanfreq= [X86-32]
|
|
See comment before function elanfreq_setup() in
|
|
arch/x86/kernel/cpu/cpufreq/elanfreq.c.
|
|
|
|
elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
|
|
Specifies physical address of start of kernel core
|
|
image elf header and optionally the size. Generally
|
|
kexec loader will pass this option to capture kernel.
|
|
See Documentation/admin-guide/kdump/kdump.rst for details.
|
|
|
|
enable_mtrr_cleanup [X86]
|
|
The kernel tries to adjust MTRR layout from continuous
|
|
to discrete, to make X server driver able to add WB
|
|
entry later. This parameter enables that.
|
|
|
|
enable_timer_pin_1 [X86]
|
|
Enable PIN 1 of APIC timer
|
|
Can be useful to work around chipset bugs
|
|
(in particular on some ATI chipsets).
|
|
The kernel tries to set a reasonable default.
|
|
|
|
enforcing [SELINUX] Set initial enforcing status.
|
|
Format: {"0" | "1"}
|
|
See security/selinux/Kconfig help text.
|
|
0 -- permissive (log only, no denials).
|
|
1 -- enforcing (deny and log).
|
|
Default value is 0.
|
|
Value can be changed at runtime via
|
|
/sys/fs/selinux/enforce.
|
|
|
|
erst_disable [ACPI]
|
|
Disable Error Record Serialization Table (ERST)
|
|
support.
|
|
|
|
ether= [HW,NET] Ethernet cards parameters
|
|
This option is obsoleted by the "netdev=" option, which
|
|
has equivalent usage. See its documentation for details.
|
|
|
|
evm= [EVM]
|
|
Format: { "fix" }
|
|
Permit 'security.evm' to be updated regardless of
|
|
current integrity status.
|
|
|
|
failslab=
|
|
fail_usercopy=
|
|
fail_page_alloc=
|
|
fail_make_request=[KNL]
|
|
General fault injection mechanism.
|
|
Format: <interval>,<probability>,<space>,<times>
|
|
See also Documentation/fault-injection/.
|
|
|
|
fb_tunnels= [NET]
|
|
Format: { initns | none }
|
|
See Documentation/admin-guide/sysctl/net.rst for
|
|
fb_tunnels_only_for_init_ns
|
|
|
|
floppy= [HW]
|
|
See Documentation/admin-guide/blockdev/floppy.rst.
|
|
|
|
force_pal_cache_flush
|
|
[IA-64] Avoid check_sal_cache_flush which may hang on
|
|
buggy SAL_CACHE_FLUSH implementations. Using this
|
|
parameter will force ia64_sal_cache_flush to call
|
|
ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
|
|
|
|
forcepae [X86-32]
|
|
Forcefully enable Physical Address Extension (PAE).
|
|
Many Pentium M systems disable PAE but may have a
|
|
functionally usable PAE implementation.
|
|
Warning: use of this parameter will taint the kernel
|
|
and may cause unknown problems.
|
|
|
|
ftrace=[tracer]
|
|
[FTRACE] will set and start the specified tracer
|
|
as early as possible in order to facilitate early
|
|
boot debugging.
|
|
|
|
ftrace_dump_on_oops[=orig_cpu]
|
|
[FTRACE] will dump the trace buffers on oops.
|
|
If no parameter is passed, ftrace will dump
|
|
buffers of all CPUs, but if you pass orig_cpu, it will
|
|
dump only the buffer of the CPU that triggered the
|
|
oops.
|
|
|
|
ftrace_filter=[function-list]
|
|
[FTRACE] Limit the functions traced by the function
|
|
tracer at boot up. function-list is a comma-separated
|
|
list of functions. This list can be changed at run
|
|
time by the set_ftrace_filter file in the debugfs
|
|
tracing directory.
|
|
|
|
ftrace_notrace=[function-list]
|
|
[FTRACE] Do not trace the functions specified in
|
|
function-list. This list can be changed at run time
|
|
by the set_ftrace_notrace file in the debugfs
|
|
tracing directory.
|
|
|
|
ftrace_graph_filter=[function-list]
|
|
[FTRACE] Limit the top level callers functions traced
|
|
by the function graph tracer at boot up.
|
|
function-list is a comma-separated list of functions
|
|
that can be changed at run time by the
|
|
set_graph_function file in the debugfs tracing directory.
|
|
|
|
ftrace_graph_notrace=[function-list]
|
|
[FTRACE] Do not trace from the functions specified in
|
|
function-list. This list is a comma-separated list of
|
|
functions that can be changed at run time by the
|
|
set_graph_notrace file in the debugfs tracing directory.
|
|
|
|
ftrace_graph_max_depth=<uint>
|
|
[FTRACE] Used with the function graph tracer. This is
|
|
the max depth it will trace into a function. This value
|
|
can be changed at run time by the max_graph_depth file
|
|
in the tracefs tracing directory. default: 0 (no limit)
|
|
|
|
fw_devlink= [KNL] Create device links between consumer and supplier
|
|
devices by scanning the firmware to infer the
|
|
consumer/supplier relationships. This feature is
|
|
especially useful when drivers are loaded as modules as
|
|
it ensures proper ordering of tasks like device probing
|
|
(suppliers first, then consumers), supplier boot state
|
|
clean up (only after all consumers have probed),
|
|
suspend/resume & runtime PM (consumers first, then
|
|
suppliers).
|
|
Format: { off | permissive | on | rpm }
|
|
off -- Don't create device links from firmware info.
|
|
permissive -- Create device links from firmware info
|
|
but use it only for ordering boot state clean
|
|
up (sync_state() calls).
|
|
on -- Create device links from firmware info and use it
|
|
to enforce probe and suspend/resume ordering.
|
|
rpm -- Like "on", but also use to order runtime PM.
|
|
|
|
fw_devlink.strict=<bool>
|
|
[KNL] Treat all inferred dependencies as mandatory
|
|
dependencies. This only applies for fw_devlink=on|rpm.
|
|
Format: <bool>
|
|
|
|
gamecon.map[2|3]=
|
|
[HW,JOY] Multisystem joystick and NES/SNES/PSX pad
|
|
support via parallel port (up to 5 devices per port)
|
|
Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
|
|
See also Documentation/input/devices/joystick-parport.rst
|
|
|
|
gamma= [HW,DRM]
|
|
|
|
gart_fix_e820= [X86-64] disable the fix e820 for K8 GART
|
|
Format: off | on
|
|
default: on
|
|
|
|
gcov_persist= [GCOV] When non-zero (default), profiling data for
|
|
kernel modules is saved and remains accessible via
|
|
debugfs, even when the module is unloaded/reloaded.
|
|
When zero, profiling data is discarded and associated
|
|
debugfs files are removed at module unload time.
|
|
|
|
goldfish [X86] Enable the goldfish android emulator platform.
|
|
Don't use this when you are not running on the
|
|
android emulator
|
|
|
|
gpt [EFI] Forces disk with valid GPT signature but
|
|
invalid Protective MBR to be treated as GPT. If the
|
|
primary GPT is corrupted, it enables the backup/alternate
|
|
GPT to be used instead.
|
|
|
|
grcan.enable0= [HW] Configuration of physical interface 0. Determines
|
|
the "Enable 0" bit of the configuration register.
|
|
Format: 0 | 1
|
|
Default: 0
|
|
grcan.enable1= [HW] Configuration of physical interface 1. Determines
|
|
the "Enable 0" bit of the configuration register.
|
|
Format: 0 | 1
|
|
Default: 0
|
|
grcan.select= [HW] Select which physical interface to use.
|
|
Format: 0 | 1
|
|
Default: 0
|
|
grcan.txsize= [HW] Sets the size of the tx buffer.
|
|
Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
|
|
Default: 1024
|
|
grcan.rxsize= [HW] Sets the size of the rx buffer.
|
|
Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
|
|
Default: 1024
|
|
|
|
gpio-mockup.gpio_mockup_ranges
|
|
[HW] Sets the ranges of gpiochip of for this device.
|
|
Format: <start1>,<end1>,<start2>,<end2>...
|
|
|
|
hardlockup_all_cpu_backtrace=
|
|
[KNL] Should the hard-lockup detector generate
|
|
backtraces on all cpus.
|
|
Format: 0 | 1
|
|
|
|
hashdist= [KNL,NUMA] Large hashes allocated during boot
|
|
are distributed across NUMA nodes. Defaults on
|
|
for 64-bit NUMA, off otherwise.
|
|
Format: 0 | 1 (for off | on)
|
|
|
|
hcl= [IA-64] SGI's Hardware Graph compatibility layer
|
|
|
|
hd= [EIDE] (E)IDE hard drive subsystem geometry
|
|
Format: <cyl>,<head>,<sect>
|
|
|
|
hest_disable [ACPI]
|
|
Disable Hardware Error Source Table (HEST) support;
|
|
corresponding firmware-first mode error processing
|
|
logic will be disabled.
|
|
|
|
highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
|
|
size of <nn>. This works even on boxes that have no
|
|
highmem otherwise. This also works to reduce highmem
|
|
size on bigger boxes.
|
|
|
|
highres= [KNL] Enable/disable high resolution timer mode.
|
|
Valid parameters: "on", "off"
|
|
Default: "on"
|
|
|
|
hlt [BUGS=ARM,SH]
|
|
|
|
hpet= [X86-32,HPET] option to control HPET usage
|
|
Format: { enable (default) | disable | force |
|
|
verbose }
|
|
disable: disable HPET and use PIT instead
|
|
force: allow force enabled of undocumented chips (ICH4,
|
|
VIA, nVidia)
|
|
verbose: show contents of HPET registers during setup
|
|
|
|
hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
|
|
registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
|
|
|
|
hugetlb_cma= [HW,CMA] The size of a CMA area used for allocation
|
|
of gigantic hugepages.
|
|
Format: nn[KMGTPE]
|
|
|
|
Reserve a CMA area of given size and allocate gigantic
|
|
hugepages using the CMA allocator. If enabled, the
|
|
boot-time allocation of gigantic hugepages is skipped.
|
|
|
|
hugepages= [HW] Number of HugeTLB pages to allocate at boot.
|
|
If this follows hugepagesz (below), it specifies
|
|
the number of pages of hugepagesz to be allocated.
|
|
If this is the first HugeTLB parameter on the command
|
|
line, it specifies the number of pages to allocate for
|
|
the default huge page size. See also
|
|
Documentation/admin-guide/mm/hugetlbpage.rst.
|
|
Format: <integer>
|
|
|
|
hugepagesz=
|
|
[HW] The size of the HugeTLB pages. This is used in
|
|
conjunction with hugepages (above) to allocate huge
|
|
pages of a specific size at boot. The pair
|
|
hugepagesz=X hugepages=Y can be specified once for
|
|
each supported huge page size. Huge page sizes are
|
|
architecture dependent. See also
|
|
Documentation/admin-guide/mm/hugetlbpage.rst.
|
|
Format: size[KMG]
|
|
|
|
hung_task_panic=
|
|
[KNL] Should the hung task detector generate panics.
|
|
Format: 0 | 1
|
|
|
|
A value of 1 instructs the kernel to panic when a
|
|
hung task is detected. The default value is controlled
|
|
by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
|
|
option. The value selected by this boot parameter can
|
|
be changed later by the kernel.hung_task_panic sysctl.
|
|
|
|
hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
|
|
terminal devices. Valid values: 0..8
|
|
hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
|
|
If specified, z/VM IUCV HVC accepts connections
|
|
from listed z/VM user IDs only.
|
|
|
|
hv_nopvspin [X86,HYPER_V] Disables the paravirt spinlock optimizations
|
|
which allow the hypervisor to 'idle' the
|
|
guest on lock contention.
|
|
|
|
keep_bootcon [KNL]
|
|
Do not unregister boot console at start. This is only
|
|
useful for debugging when something happens in the window
|
|
between unregistering the boot console and initializing
|
|
the real console.
|
|
|
|
i2c_bus= [HW] Override the default board specific I2C bus speed
|
|
or register an additional I2C bus that is not
|
|
registered from board initialization code.
|
|
Format:
|
|
<bus_id>,<clkrate>
|
|
|
|
i8042.debug [HW] Toggle i8042 debug mode
|
|
i8042.unmask_kbd_data
|
|
[HW] Enable printing of interrupt data from the KBD port
|
|
(disabled by default, and as a pre-condition
|
|
requires that i8042.debug=1 be enabled)
|
|
i8042.direct [HW] Put keyboard port into non-translated mode
|
|
i8042.dumbkbd [HW] Pretend that controller can only read data from
|
|
keyboard and cannot control its state
|
|
(Don't attempt to blink the leds)
|
|
i8042.noaux [HW] Don't check for auxiliary (== mouse) port
|
|
i8042.nokbd [HW] Don't check/create keyboard port
|
|
i8042.noloop [HW] Disable the AUX Loopback command while probing
|
|
for the AUX port
|
|
i8042.nomux [HW] Don't check presence of an active multiplexing
|
|
controller
|
|
i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
|
|
controllers
|
|
i8042.notimeout [HW] Ignore timeout condition signalled by controller
|
|
i8042.reset [HW] Reset the controller during init, cleanup and
|
|
suspend-to-ram transitions, only during s2r
|
|
transitions, or never reset
|
|
Format: { 1 | Y | y | 0 | N | n }
|
|
1, Y, y: always reset controller
|
|
0, N, n: don't ever reset controller
|
|
Default: only on s2r transitions on x86; most other
|
|
architectures force reset to be always executed
|
|
i8042.unlock [HW] Unlock (ignore) the keylock
|
|
i8042.kbdreset [HW] Reset device connected to KBD port
|
|
|
|
i810= [HW,DRM]
|
|
|
|
i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
|
|
indicates that the driver is running on unsupported
|
|
hardware.
|
|
i8k.force [HW] Activate i8k driver even if SMM BIOS signature
|
|
does not match list of supported models.
|
|
i8k.power_status
|
|
[HW] Report power status in /proc/i8k
|
|
(disabled by default)
|
|
i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
|
|
capability is set.
|
|
|
|
i915.invert_brightness=
|
|
[DRM] Invert the sense of the variable that is used to
|
|
set the brightness of the panel backlight. Normally a
|
|
brightness value of 0 indicates backlight switched off,
|
|
and the maximum of the brightness value sets the backlight
|
|
to maximum brightness. If this parameter is set to 0
|
|
(default) and the machine requires it, or this parameter
|
|
is set to 1, a brightness value of 0 sets the backlight
|
|
to maximum brightness, and the maximum of the brightness
|
|
value switches the backlight off.
|
|
-1 -- never invert brightness
|
|
0 -- machine default
|
|
1 -- force brightness inversion
|
|
|
|
icn= [HW,ISDN]
|
|
Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
|
|
|
|
ide-core.nodma= [HW] (E)IDE subsystem
|
|
Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
|
|
.vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
|
|
.cdrom .chs .ignore_cable are additional options
|
|
See Documentation/ide/ide.rst.
|
|
|
|
ide-generic.probe-mask= [HW] (E)IDE subsystem
|
|
Format: <int>
|
|
Probe mask for legacy ISA IDE ports. Depending on
|
|
platform up to 6 ports are supported, enabled by
|
|
setting corresponding bits in the mask to 1. The
|
|
default value is 0x0, which has a special meaning.
|
|
On systems that have PCI, it triggers scanning the
|
|
PCI bus for the first and the second port, which
|
|
are then probed. On systems without PCI the value
|
|
of 0x0 enables probing the two first ports as if it
|
|
was 0x3.
|
|
|
|
ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
|
|
Claim all unknown PCI IDE storage controllers.
|
|
|
|
idle= [X86]
|
|
Format: idle=poll, idle=halt, idle=nomwait
|
|
Poll forces a polling idle loop that can slightly
|
|
improve the performance of waking up a idle CPU, but
|
|
will use a lot of power and make the system run hot.
|
|
Not recommended.
|
|
idle=halt: Halt is forced to be used for CPU idle.
|
|
In such case C2/C3 won't be used again.
|
|
idle=nomwait: Disable mwait for CPU C-states
|
|
|
|
idxd.sva= [HW]
|
|
Format: <bool>
|
|
Allow force disabling of Shared Virtual Memory (SVA)
|
|
support for the idxd driver. By default it is set to
|
|
true (1).
|
|
|
|
ieee754= [MIPS] Select IEEE Std 754 conformance mode
|
|
Format: { strict | legacy | 2008 | relaxed }
|
|
Default: strict
|
|
|
|
Choose which programs will be accepted for execution
|
|
based on the IEEE 754 NaN encoding(s) supported by
|
|
the FPU and the NaN encoding requested with the value
|
|
of an ELF file header flag individually set by each
|
|
binary. Hardware implementations are permitted to
|
|
support either or both of the legacy and the 2008 NaN
|
|
encoding mode.
|
|
|
|
Available settings are as follows:
|
|
strict accept binaries that request a NaN encoding
|
|
supported by the FPU
|
|
legacy only accept legacy-NaN binaries, if supported
|
|
by the FPU
|
|
2008 only accept 2008-NaN binaries, if supported
|
|
by the FPU
|
|
relaxed accept any binaries regardless of whether
|
|
supported by the FPU
|
|
|
|
The FPU emulator is always able to support both NaN
|
|
encodings, so if no FPU hardware is present or it has
|
|
been disabled with 'nofpu', then the settings of
|
|
'legacy' and '2008' strap the emulator accordingly,
|
|
'relaxed' straps the emulator for both legacy-NaN and
|
|
2008-NaN, whereas 'strict' enables legacy-NaN only on
|
|
legacy processors and both NaN encodings on MIPS32 or
|
|
MIPS64 CPUs.
|
|
|
|
The setting for ABS.fmt/NEG.fmt instruction execution
|
|
mode generally follows that for the NaN encoding,
|
|
except where unsupported by hardware.
|
|
|
|
ignore_loglevel [KNL]
|
|
Ignore loglevel setting - this will print /all/
|
|
kernel messages to the console. Useful for debugging.
|
|
We also add it as printk module parameter, so users
|
|
could change it dynamically, usually by
|
|
/sys/module/printk/parameters/ignore_loglevel.
|
|
|
|
ignore_rlimit_data
|
|
Ignore RLIMIT_DATA setting for data mappings,
|
|
print warning at first misuse. Can be changed via
|
|
/sys/module/kernel/parameters/ignore_rlimit_data.
|
|
|
|
ihash_entries= [KNL]
|
|
Set number of hash buckets for inode cache.
|
|
|
|
ima_appraise= [IMA] appraise integrity measurements
|
|
Format: { "off" | "enforce" | "fix" | "log" }
|
|
default: "enforce"
|
|
|
|
ima_appraise_tcb [IMA] Deprecated. Use ima_policy= instead.
|
|
The builtin appraise policy appraises all files
|
|
owned by uid=0.
|
|
|
|
ima_canonical_fmt [IMA]
|
|
Use the canonical format for the binary runtime
|
|
measurements, instead of host native format.
|
|
|
|
ima_hash= [IMA]
|
|
Format: { md5 | sha1 | rmd160 | sha256 | sha384
|
|
| sha512 | ... }
|
|
default: "sha1"
|
|
|
|
The list of supported hash algorithms is defined
|
|
in crypto/hash_info.h.
|
|
|
|
ima_policy= [IMA]
|
|
The builtin policies to load during IMA setup.
|
|
Format: "tcb | appraise_tcb | secure_boot |
|
|
fail_securely | critical_data"
|
|
|
|
The "tcb" policy measures all programs exec'd, files
|
|
mmap'd for exec, and all files opened with the read
|
|
mode bit set by either the effective uid (euid=0) or
|
|
uid=0.
|
|
|
|
The "appraise_tcb" policy appraises the integrity of
|
|
all files owned by root.
|
|
|
|
The "secure_boot" policy appraises the integrity
|
|
of files (eg. kexec kernel image, kernel modules,
|
|
firmware, policy, etc) based on file signatures.
|
|
|
|
The "fail_securely" policy forces file signature
|
|
verification failure also on privileged mounted
|
|
filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
|
|
flag.
|
|
|
|
The "critical_data" policy measures kernel integrity
|
|
critical data.
|
|
|
|
ima_tcb [IMA] Deprecated. Use ima_policy= instead.
|
|
Load a policy which meets the needs of the Trusted
|
|
Computing Base. This means IMA will measure all
|
|
programs exec'd, files mmap'd for exec, and all files
|
|
opened for read by uid=0.
|
|
|
|
ima_template= [IMA]
|
|
Select one of defined IMA measurements template formats.
|
|
Formats: { "ima" | "ima-ng" | "ima-sig" }
|
|
Default: "ima-ng"
|
|
|
|
ima_template_fmt=
|
|
[IMA] Define a custom template format.
|
|
Format: { "field1|...|fieldN" }
|
|
|
|
ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
|
|
Format: <min_file_size>
|
|
Set the minimal file size for using asynchronous hash.
|
|
If left unspecified, ahash usage is disabled.
|
|
|
|
ahash performance varies for different data sizes on
|
|
different crypto accelerators. This option can be used
|
|
to achieve the best performance for a particular HW.
|
|
|
|
ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
|
|
Format: <bufsize>
|
|
Set hashing buffer size. Default: 4k.
|
|
|
|
ahash performance varies for different chunk sizes on
|
|
different crypto accelerators. This option can be used
|
|
to achieve best performance for particular HW.
|
|
|
|
init= [KNL]
|
|
Format: <full_path>
|
|
Run specified binary instead of /sbin/init as init
|
|
process.
|
|
|
|
initcall_debug [KNL] Trace initcalls as they are executed. Useful
|
|
for working out where the kernel is dying during
|
|
startup.
|
|
|
|
initcall_blacklist= [KNL] Do not execute a comma-separated list of
|
|
initcall functions. Useful for debugging built-in
|
|
modules and initcalls.
|
|
|
|
initrd= [BOOT] Specify the location of the initial ramdisk
|
|
|
|
initrdmem= [KNL] Specify a physical address and size from which to
|
|
load the initrd. If an initrd is compiled in or
|
|
specified in the bootparams, it takes priority over this
|
|
setting.
|
|
Format: ss[KMG],nn[KMG]
|
|
Default is 0, 0
|
|
|
|
init_on_alloc= [MM] Fill newly allocated pages and heap objects with
|
|
zeroes.
|
|
Format: 0 | 1
|
|
Default set by CONFIG_INIT_ON_ALLOC_DEFAULT_ON.
|
|
|
|
init_on_free= [MM] Fill freed pages and heap objects with zeroes.
|
|
Format: 0 | 1
|
|
Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON.
|
|
|
|
init_pkru= [X86] Specify the default memory protection keys rights
|
|
register contents for all processes. 0x55555554 by
|
|
default (disallow access to all but pkey 0). Can
|
|
override in debugfs after boot.
|
|
|
|
inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
|
|
Format: <irq>
|
|
|
|
int_pln_enable [X86] Enable power limit notification interrupt
|
|
|
|
integrity_audit=[IMA]
|
|
Format: { "0" | "1" }
|
|
0 -- basic integrity auditing messages. (Default)
|
|
1 -- additional integrity auditing messages.
|
|
|
|
intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
|
|
on
|
|
Enable intel iommu driver.
|
|
off
|
|
Disable intel iommu driver.
|
|
igfx_off [Default Off]
|
|
By default, gfx is mapped as normal device. If a gfx
|
|
device has a dedicated DMAR unit, the DMAR unit is
|
|
bypassed by not enabling DMAR with this option. In
|
|
this case, gfx device will use physical address for
|
|
DMA.
|
|
forcedac [X86-64]
|
|
With this option iommu will not optimize to look
|
|
for io virtual address below 32-bit forcing dual
|
|
address cycle on pci bus for cards supporting greater
|
|
than 32-bit addressing. The default is to look
|
|
for translation below 32-bit and if not available
|
|
then look in the higher range.
|
|
strict [Default Off]
|
|
With this option on every unmap_single operation will
|
|
result in a hardware IOTLB flush operation as opposed
|
|
to batching them for performance.
|
|
sp_off [Default Off]
|
|
By default, super page will be supported if Intel IOMMU
|
|
has the capability. With this option, super page will
|
|
not be supported.
|
|
sm_on [Default Off]
|
|
By default, scalable mode will be disabled even if the
|
|
hardware advertises that it has support for the scalable
|
|
mode translation. With this option set, scalable mode
|
|
will be used on hardware which claims to support it.
|
|
tboot_noforce [Default Off]
|
|
Do not force the Intel IOMMU enabled under tboot.
|
|
By default, tboot will force Intel IOMMU on, which
|
|
could harm performance of some high-throughput
|
|
devices like 40GBit network cards, even if identity
|
|
mapping is enabled.
|
|
Note that using this option lowers the security
|
|
provided by tboot because it makes the system
|
|
vulnerable to DMA attacks.
|
|
|
|
intel_idle.max_cstate= [KNL,HW,ACPI,X86]
|
|
0 disables intel_idle and fall back on acpi_idle.
|
|
1 to 9 specify maximum depth of C-state.
|
|
|
|
intel_pstate= [X86]
|
|
disable
|
|
Do not enable intel_pstate as the default
|
|
scaling driver for the supported processors
|
|
passive
|
|
Use intel_pstate as a scaling driver, but configure it
|
|
to work with generic cpufreq governors (instead of
|
|
enabling its internal governor). This mode cannot be
|
|
used along with the hardware-managed P-states (HWP)
|
|
feature.
|
|
force
|
|
Enable intel_pstate on systems that prohibit it by default
|
|
in favor of acpi-cpufreq. Forcing the intel_pstate driver
|
|
instead of acpi-cpufreq may disable platform features, such
|
|
as thermal controls and power capping, that rely on ACPI
|
|
P-States information being indicated to OSPM and therefore
|
|
should be used with caution. This option does not work with
|
|
processors that aren't supported by the intel_pstate driver
|
|
or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
|
|
no_hwp
|
|
Do not enable hardware P state control (HWP)
|
|
if available.
|
|
hwp_only
|
|
Only load intel_pstate on systems which support
|
|
hardware P state control (HWP) if available.
|
|
support_acpi_ppc
|
|
Enforce ACPI _PPC performance limits. If the Fixed ACPI
|
|
Description Table, specifies preferred power management
|
|
profile as "Enterprise Server" or "Performance Server",
|
|
then this feature is turned on by default.
|
|
per_cpu_perf_limits
|
|
Allow per-logical-CPU P-State performance control limits using
|
|
cpufreq sysfs interface
|
|
|
|
intremap= [X86-64, Intel-IOMMU]
|
|
on enable Interrupt Remapping (default)
|
|
off disable Interrupt Remapping
|
|
nosid disable Source ID checking
|
|
no_x2apic_optout
|
|
BIOS x2APIC opt-out request will be ignored
|
|
nopost disable Interrupt Posting
|
|
|
|
iomem= Disable strict checking of access to MMIO memory
|
|
strict regions from userspace.
|
|
relaxed
|
|
|
|
iommu= [X86]
|
|
off
|
|
force
|
|
noforce
|
|
biomerge
|
|
panic
|
|
nopanic
|
|
merge
|
|
nomerge
|
|
soft
|
|
pt [X86]
|
|
nopt [X86]
|
|
nobypass [PPC/POWERNV]
|
|
Disable IOMMU bypass, using IOMMU for PCI devices.
|
|
|
|
iommu.strict= [ARM64] Configure TLB invalidation behaviour
|
|
Format: { "0" | "1" }
|
|
0 - Lazy mode.
|
|
Request that DMA unmap operations use deferred
|
|
invalidation of hardware TLBs, for increased
|
|
throughput at the cost of reduced device isolation.
|
|
Will fall back to strict mode if not supported by
|
|
the relevant IOMMU driver.
|
|
1 - Strict mode (default).
|
|
DMA unmap operations invalidate IOMMU hardware TLBs
|
|
synchronously.
|
|
|
|
iommu.passthrough=
|
|
[ARM64, X86] Configure DMA to bypass the IOMMU by default.
|
|
Format: { "0" | "1" }
|
|
0 - Use IOMMU translation for DMA.
|
|
1 - Bypass the IOMMU for DMA.
|
|
unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
|
|
|
|
io7= [HW] IO7 for Marvel-based Alpha systems
|
|
See comment before marvel_specify_io7 in
|
|
arch/alpha/kernel/core_marvel.c.
|
|
|
|
io_delay= [X86] I/O delay method
|
|
0x80
|
|
Standard port 0x80 based delay
|
|
0xed
|
|
Alternate port 0xed based delay (needed on some systems)
|
|
udelay
|
|
Simple two microseconds delay
|
|
none
|
|
No delay
|
|
|
|
ip= [IP_PNP]
|
|
See Documentation/admin-guide/nfs/nfsroot.rst.
|
|
|
|
ipcmni_extend [KNL] Extend the maximum number of unique System V
|
|
IPC identifiers from 32,768 to 16,777,216.
|
|
|
|
irqaffinity= [SMP] Set the default irq affinity mask
|
|
The argument is a cpu list, as described above.
|
|
|
|
irqchip.gicv2_force_probe=
|
|
[ARM, ARM64]
|
|
Format: <bool>
|
|
Force the kernel to look for the second 4kB page
|
|
of a GICv2 controller even if the memory range
|
|
exposed by the device tree is too small.
|
|
|
|
irqchip.gicv3_nolpi=
|
|
[ARM, ARM64]
|
|
Force the kernel to ignore the availability of
|
|
LPIs (and by consequence ITSs). Intended for system
|
|
that use the kernel as a bootloader, and thus want
|
|
to let secondary kernels in charge of setting up
|
|
LPIs.
|
|
|
|
irqchip.gicv3_pseudo_nmi= [ARM64]
|
|
Enables support for pseudo-NMIs in the kernel. This
|
|
requires the kernel to be built with
|
|
CONFIG_ARM64_PSEUDO_NMI.
|
|
|
|
irqfixup [HW]
|
|
When an interrupt is not handled search all handlers
|
|
for it. Intended to get systems with badly broken
|
|
firmware running.
|
|
|
|
irqpoll [HW]
|
|
When an interrupt is not handled search all handlers
|
|
for it. Also check all handlers each timer
|
|
interrupt. Intended to get systems with badly broken
|
|
firmware running.
|
|
|
|
isapnp= [ISAPNP]
|
|
Format: <RDP>,<reset>,<pci_scan>,<verbosity>
|
|
|
|
isolcpus= [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
|
|
[Deprecated - use cpusets instead]
|
|
Format: [flag-list,]<cpu-list>
|
|
|
|
Specify one or more CPUs to isolate from disturbances
|
|
specified in the flag list (default: domain):
|
|
|
|
nohz
|
|
Disable the tick when a single task runs.
|
|
|
|
A residual 1Hz tick is offloaded to workqueues, which you
|
|
need to affine to housekeeping through the global
|
|
workqueue's affinity configured via the
|
|
/sys/devices/virtual/workqueue/cpumask sysfs file, or
|
|
by using the 'domain' flag described below.
|
|
|
|
NOTE: by default the global workqueue runs on all CPUs,
|
|
so to protect individual CPUs the 'cpumask' file has to
|
|
be configured manually after bootup.
|
|
|
|
domain
|
|
Isolate from the general SMP balancing and scheduling
|
|
algorithms. Note that performing domain isolation this way
|
|
is irreversible: it's not possible to bring back a CPU to
|
|
the domains once isolated through isolcpus. It's strongly
|
|
advised to use cpusets instead to disable scheduler load
|
|
balancing through the "cpuset.sched_load_balance" file.
|
|
It offers a much more flexible interface where CPUs can
|
|
move in and out of an isolated set anytime.
|
|
|
|
You can move a process onto or off an "isolated" CPU via
|
|
the CPU affinity syscalls or cpuset.
|
|
<cpu number> begins at 0 and the maximum value is
|
|
"number of CPUs in system - 1".
|
|
|
|
managed_irq
|
|
|
|
Isolate from being targeted by managed interrupts
|
|
which have an interrupt mask containing isolated
|
|
CPUs. The affinity of managed interrupts is
|
|
handled by the kernel and cannot be changed via
|
|
the /proc/irq/* interfaces.
|
|
|
|
This isolation is best effort and only effective
|
|
if the automatically assigned interrupt mask of a
|
|
device queue contains isolated and housekeeping
|
|
CPUs. If housekeeping CPUs are online then such
|
|
interrupts are directed to the housekeeping CPU
|
|
so that IO submitted on the housekeeping CPU
|
|
cannot disturb the isolated CPU.
|
|
|
|
If a queue's affinity mask contains only isolated
|
|
CPUs then this parameter has no effect on the
|
|
interrupt routing decision, though interrupts are
|
|
only delivered when tasks running on those
|
|
isolated CPUs submit IO. IO submitted on
|
|
housekeeping CPUs has no influence on those
|
|
queues.
|
|
|
|
The format of <cpu-list> is described above.
|
|
|
|
iucv= [HW,NET]
|
|
|
|
ivrs_ioapic [HW,X86-64]
|
|
Provide an override to the IOAPIC-ID<->DEVICE-ID
|
|
mapping provided in the IVRS ACPI table. For
|
|
example, to map IOAPIC-ID decimal 10 to
|
|
PCI device 00:14.0 write the parameter as:
|
|
ivrs_ioapic[10]=00:14.0
|
|
|
|
ivrs_hpet [HW,X86-64]
|
|
Provide an override to the HPET-ID<->DEVICE-ID
|
|
mapping provided in the IVRS ACPI table. For
|
|
example, to map HPET-ID decimal 0 to
|
|
PCI device 00:14.0 write the parameter as:
|
|
ivrs_hpet[0]=00:14.0
|
|
|
|
ivrs_acpihid [HW,X86-64]
|
|
Provide an override to the ACPI-HID:UID<->DEVICE-ID
|
|
mapping provided in the IVRS ACPI table. For
|
|
example, to map UART-HID:UID AMD0020:0 to
|
|
PCI device 00:14.5 write the parameter as:
|
|
ivrs_acpihid[00:14.5]=AMD0020:0
|
|
|
|
js= [HW,JOY] Analog joystick
|
|
See Documentation/input/joydev/joystick.rst.
|
|
|
|
nokaslr [KNL]
|
|
When CONFIG_RANDOMIZE_BASE is set, this disables
|
|
kernel and module base offset ASLR (Address Space
|
|
Layout Randomization).
|
|
|
|
kasan_multi_shot
|
|
[KNL] Enforce KASAN (Kernel Address Sanitizer) to print
|
|
report on every invalid memory access. Without this
|
|
parameter KASAN will print report only for the first
|
|
invalid access.
|
|
|
|
keepinitrd [HW,ARM]
|
|
|
|
kernelcore= [KNL,X86,IA-64,PPC]
|
|
Format: nn[KMGTPE] | nn% | "mirror"
|
|
This parameter specifies the amount of memory usable by
|
|
the kernel for non-movable allocations. The requested
|
|
amount is spread evenly throughout all nodes in the
|
|
system as ZONE_NORMAL. The remaining memory is used for
|
|
movable memory in its own zone, ZONE_MOVABLE. In the
|
|
event, a node is too small to have both ZONE_NORMAL and
|
|
ZONE_MOVABLE, kernelcore memory will take priority and
|
|
other nodes will have a larger ZONE_MOVABLE.
|
|
|
|
ZONE_MOVABLE is used for the allocation of pages that
|
|
may be reclaimed or moved by the page migration
|
|
subsystem. Note that allocations like PTEs-from-HighMem
|
|
still use the HighMem zone if it exists, and the Normal
|
|
zone if it does not.
|
|
|
|
It is possible to specify the exact amount of memory in
|
|
the form of "nn[KMGTPE]", a percentage of total system
|
|
memory in the form of "nn%", or "mirror". If "mirror"
|
|
option is specified, mirrored (reliable) memory is used
|
|
for non-movable allocations and remaining memory is used
|
|
for Movable pages. "nn[KMGTPE]", "nn%", and "mirror"
|
|
are exclusive, so you cannot specify multiple forms.
|
|
|
|
kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
|
|
Format: <Controller#>[,poll interval]
|
|
The controller # is the number of the ehci usb debug
|
|
port as it is probed via PCI. The poll interval is
|
|
optional and is the number seconds in between
|
|
each poll cycle to the debug port in case you need
|
|
the functionality for interrupting the kernel with
|
|
gdb or control-c on the dbgp connection. When
|
|
not using this parameter you use sysrq-g to break into
|
|
the kernel debugger.
|
|
|
|
kgdboc= [KGDB,HW] kgdb over consoles.
|
|
Requires a tty driver that supports console polling,
|
|
or a supported polling keyboard driver (non-usb).
|
|
Serial only format: <serial_device>[,baud]
|
|
keyboard only format: kbd
|
|
keyboard and serial format: kbd,<serial_device>[,baud]
|
|
Optional Kernel mode setting:
|
|
kms, kbd format: kms,kbd
|
|
kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
|
|
|
|
kgdboc_earlycon= [KGDB,HW]
|
|
If the boot console provides the ability to read
|
|
characters and can work in polling mode, you can use
|
|
this parameter to tell kgdb to use it as a backend
|
|
until the normal console is registered. Intended to
|
|
be used together with the kgdboc parameter which
|
|
specifies the normal console to transition to.
|
|
|
|
The name of the early console should be specified
|
|
as the value of this parameter. Note that the name of
|
|
the early console might be different than the tty
|
|
name passed to kgdboc. It's OK to leave the value
|
|
blank and the first boot console that implements
|
|
read() will be picked.
|
|
|
|
kgdbwait [KGDB] Stop kernel execution and enter the
|
|
kernel debugger at the earliest opportunity.
|
|
|
|
kmac= [MIPS] Korina ethernet MAC address.
|
|
Configure the RouterBoard 532 series on-chip
|
|
Ethernet adapter MAC address.
|
|
|
|
kmemleak= [KNL] Boot-time kmemleak enable/disable
|
|
Valid arguments: on, off
|
|
Default: on
|
|
Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
|
|
the default is off.
|
|
|
|
kprobe_event=[probe-list]
|
|
[FTRACE] Add kprobe events and enable at boot time.
|
|
The probe-list is a semicolon delimited list of probe
|
|
definitions. Each definition is same as kprobe_events
|
|
interface, but the parameters are comma delimited.
|
|
For example, to add a kprobe event on vfs_read with
|
|
arg1 and arg2, add to the command line;
|
|
|
|
kprobe_event=p,vfs_read,$arg1,$arg2
|
|
|
|
See also Documentation/trace/kprobetrace.rst "Kernel
|
|
Boot Parameter" section.
|
|
|
|
kpti= [ARM64] Control page table isolation of user
|
|
and kernel address spaces.
|
|
Default: enabled on cores which need mitigation.
|
|
0: force disabled
|
|
1: force enabled
|
|
|
|
kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
|
|
Default is 0 (don't ignore, but inject #GP)
|
|
|
|
kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface.
|
|
Default is false (don't support).
|
|
|
|
kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
|
|
KVM MMU at runtime.
|
|
Default is 0 (off)
|
|
|
|
kvm.nx_huge_pages=
|
|
[KVM] Controls the software workaround for the
|
|
X86_BUG_ITLB_MULTIHIT bug.
|
|
force : Always deploy workaround.
|
|
off : Never deploy workaround.
|
|
auto : Deploy workaround based on the presence of
|
|
X86_BUG_ITLB_MULTIHIT.
|
|
|
|
Default is 'auto'.
|
|
|
|
If the software workaround is enabled for the host,
|
|
guests do need not to enable it for nested guests.
|
|
|
|
kvm.nx_huge_pages_recovery_ratio=
|
|
[KVM] Controls how many 4KiB pages are periodically zapped
|
|
back to huge pages. 0 disables the recovery, otherwise if
|
|
the value is N KVM will zap 1/Nth of the 4KiB pages every
|
|
minute. The default is 60.
|
|
|
|
kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
|
|
Default is 1 (enabled)
|
|
|
|
kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
|
|
for all guests.
|
|
Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
|
|
|
|
kvm-arm.mode=
|
|
[KVM,ARM] Select one of KVM/arm64's modes of operation.
|
|
|
|
nvhe: Standard nVHE-based mode, without support for
|
|
protected guests.
|
|
|
|
protected: nVHE-based mode with support for guests whose
|
|
state is kept private from the host.
|
|
Not valid if the kernel is running in EL2.
|
|
|
|
Defaults to VHE/nVHE based on hardware support.
|
|
|
|
kvm-arm.vgic_v3_group0_trap=
|
|
[KVM,ARM] Trap guest accesses to GICv3 group-0
|
|
system registers
|
|
|
|
kvm-arm.vgic_v3_group1_trap=
|
|
[KVM,ARM] Trap guest accesses to GICv3 group-1
|
|
system registers
|
|
|
|
kvm-arm.vgic_v3_common_trap=
|
|
[KVM,ARM] Trap guest accesses to GICv3 common
|
|
system registers
|
|
|
|
kvm-arm.vgic_v4_enable=
|
|
[KVM,ARM] Allow use of GICv4 for direct injection of
|
|
LPIs.
|
|
|
|
kvm_cma_resv_ratio=n [PPC]
|
|
Reserves given percentage from system memory area for
|
|
contiguous memory allocation for KVM hash pagetable
|
|
allocation.
|
|
By default it reserves 5% of total system memory.
|
|
Format: <integer>
|
|
Default: 5
|
|
|
|
kvm-intel.ept= [KVM,Intel] Disable extended page tables
|
|
(virtualized MMU) support on capable Intel chips.
|
|
Default is 1 (enabled)
|
|
|
|
kvm-intel.emulate_invalid_guest_state=
|
|
[KVM,Intel] Enable emulation of invalid guest states
|
|
Default is 0 (disabled)
|
|
|
|
kvm-intel.flexpriority=
|
|
[KVM,Intel] Disable FlexPriority feature (TPR shadow).
|
|
Default is 1 (enabled)
|
|
|
|
kvm-intel.nested=
|
|
[KVM,Intel] Enable VMX nesting (nVMX).
|
|
Default is 0 (disabled)
|
|
|
|
kvm-intel.unrestricted_guest=
|
|
[KVM,Intel] Disable unrestricted guest feature
|
|
(virtualized real and unpaged mode) on capable
|
|
Intel chips. Default is 1 (enabled)
|
|
|
|
kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
|
|
CVE-2018-3620.
|
|
|
|
Valid arguments: never, cond, always
|
|
|
|
always: L1D cache flush on every VMENTER.
|
|
cond: Flush L1D on VMENTER only when the code between
|
|
VMEXIT and VMENTER can leak host memory.
|
|
never: Disables the mitigation
|
|
|
|
Default is cond (do L1 cache flush in specific instances)
|
|
|
|
kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
|
|
feature (tagged TLBs) on capable Intel chips.
|
|
Default is 1 (enabled)
|
|
|
|
l1tf= [X86] Control mitigation of the L1TF vulnerability on
|
|
affected CPUs
|
|
|
|
The kernel PTE inversion protection is unconditionally
|
|
enabled and cannot be disabled.
|
|
|
|
full
|
|
Provides all available mitigations for the
|
|
L1TF vulnerability. Disables SMT and
|
|
enables all mitigations in the
|
|
hypervisors, i.e. unconditional L1D flush.
|
|
|
|
SMT control and L1D flush control via the
|
|
sysfs interface is still possible after
|
|
boot. Hypervisors will issue a warning
|
|
when the first VM is started in a
|
|
potentially insecure configuration,
|
|
i.e. SMT enabled or L1D flush disabled.
|
|
|
|
full,force
|
|
Same as 'full', but disables SMT and L1D
|
|
flush runtime control. Implies the
|
|
'nosmt=force' command line option.
|
|
(i.e. sysfs control of SMT is disabled.)
|
|
|
|
flush
|
|
Leaves SMT enabled and enables the default
|
|
hypervisor mitigation, i.e. conditional
|
|
L1D flush.
|
|
|
|
SMT control and L1D flush control via the
|
|
sysfs interface is still possible after
|
|
boot. Hypervisors will issue a warning
|
|
when the first VM is started in a
|
|
potentially insecure configuration,
|
|
i.e. SMT enabled or L1D flush disabled.
|
|
|
|
flush,nosmt
|
|
|
|
Disables SMT and enables the default
|
|
hypervisor mitigation.
|
|
|
|
SMT control and L1D flush control via the
|
|
sysfs interface is still possible after
|
|
boot. Hypervisors will issue a warning
|
|
when the first VM is started in a
|
|
potentially insecure configuration,
|
|
i.e. SMT enabled or L1D flush disabled.
|
|
|
|
flush,nowarn
|
|
Same as 'flush', but hypervisors will not
|
|
warn when a VM is started in a potentially
|
|
insecure configuration.
|
|
|
|
off
|
|
Disables hypervisor mitigations and doesn't
|
|
emit any warnings.
|
|
It also drops the swap size and available
|
|
RAM limit restriction on both hypervisor and
|
|
bare metal.
|
|
|
|
Default is 'flush'.
|
|
|
|
For details see: Documentation/admin-guide/hw-vuln/l1tf.rst
|
|
|
|
l2cr= [PPC]
|
|
|
|
l3cr= [PPC]
|
|
|
|
lapic [X86-32,APIC] Enable the local APIC even if BIOS
|
|
disabled it.
|
|
|
|
lapic= [X86,APIC] Do not use TSC deadline
|
|
value for LAPIC timer one-shot implementation. Default
|
|
back to the programmable timer unit in the LAPIC.
|
|
Format: notscdeadline
|
|
|
|
lapic_timer_c2_ok [X86,APIC] trust the local apic timer
|
|
in C2 power state.
|
|
|
|
libata.dma= [LIBATA] DMA control
|
|
libata.dma=0 Disable all PATA and SATA DMA
|
|
libata.dma=1 PATA and SATA Disk DMA only
|
|
libata.dma=2 ATAPI (CDROM) DMA only
|
|
libata.dma=4 Compact Flash DMA only
|
|
Combinations also work, so libata.dma=3 enables DMA
|
|
for disks and CDROMs, but not CFs.
|
|
|
|
libata.ignore_hpa= [LIBATA] Ignore HPA limit
|
|
libata.ignore_hpa=0 keep BIOS limits (default)
|
|
libata.ignore_hpa=1 ignore limits, using full disk
|
|
|
|
libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
|
|
when set.
|
|
Format: <int>
|
|
|
|
libata.force= [LIBATA] Force configurations. The format is comma-
|
|
separated list of "[ID:]VAL" where ID is
|
|
PORT[.DEVICE]. PORT and DEVICE are decimal numbers
|
|
matching port, link or device. Basically, it matches
|
|
the ATA ID string printed on console by libata. If
|
|
the whole ID part is omitted, the last PORT and DEVICE
|
|
values are used. If ID hasn't been specified yet, the
|
|
configuration applies to all ports, links and devices.
|
|
|
|
If only DEVICE is omitted, the parameter applies to
|
|
the port and all links and devices behind it. DEVICE
|
|
number of 0 either selects the first device or the
|
|
first fan-out link behind PMP device. It does not
|
|
select the host link. DEVICE number of 15 selects the
|
|
host link and device attached to it.
|
|
|
|
The VAL specifies the configuration to force. As long
|
|
as there's no ambiguity shortcut notation is allowed.
|
|
For example, both 1.5 and 1.5G would work for 1.5Gbps.
|
|
The following configurations can be forced.
|
|
|
|
* Cable type: 40c, 80c, short40c, unk, ign or sata.
|
|
Any ID with matching PORT is used.
|
|
|
|
* SATA link speed limit: 1.5Gbps or 3.0Gbps.
|
|
|
|
* Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
|
|
udma[/][16,25,33,44,66,100,133] notation is also
|
|
allowed.
|
|
|
|
* [no]ncq: Turn on or off NCQ.
|
|
|
|
* [no]ncqtrim: Turn off queued DSM TRIM.
|
|
|
|
* nohrst, nosrst, norst: suppress hard, soft
|
|
and both resets.
|
|
|
|
* rstonce: only attempt one reset during
|
|
hot-unplug link recovery
|
|
|
|
* dump_id: dump IDENTIFY data.
|
|
|
|
* atapi_dmadir: Enable ATAPI DMADIR bridge support
|
|
|
|
* disable: Disable this device.
|
|
|
|
If there are multiple matching configurations changing
|
|
the same attribute, the last one is used.
|
|
|
|
memblock=debug [KNL] Enable memblock debug messages.
|
|
|
|
load_ramdisk= [RAM] [Deprecated]
|
|
|
|
lockd.nlm_grace_period=P [NFS] Assign grace period.
|
|
Format: <integer>
|
|
|
|
lockd.nlm_tcpport=N [NFS] Assign TCP port.
|
|
Format: <integer>
|
|
|
|
lockd.nlm_timeout=T [NFS] Assign timeout value.
|
|
Format: <integer>
|
|
|
|
lockd.nlm_udpport=M [NFS] Assign UDP port.
|
|
Format: <integer>
|
|
|
|
lockdown= [SECURITY]
|
|
{ integrity | confidentiality }
|
|
Enable the kernel lockdown feature. If set to
|
|
integrity, kernel features that allow userland to
|
|
modify the running kernel are disabled. If set to
|
|
confidentiality, kernel features that allow userland
|
|
to extract confidential information from the kernel
|
|
are also disabled.
|
|
|
|
locktorture.nreaders_stress= [KNL]
|
|
Set the number of locking read-acquisition kthreads.
|
|
Defaults to being automatically set based on the
|
|
number of online CPUs.
|
|
|
|
locktorture.nwriters_stress= [KNL]
|
|
Set the number of locking write-acquisition kthreads.
|
|
|
|
locktorture.onoff_holdoff= [KNL]
|
|
Set time (s) after boot for CPU-hotplug testing.
|
|
|
|
locktorture.onoff_interval= [KNL]
|
|
Set time (s) between CPU-hotplug operations, or
|
|
zero to disable CPU-hotplug testing.
|
|
|
|
locktorture.shuffle_interval= [KNL]
|
|
Set task-shuffle interval (jiffies). Shuffling
|
|
tasks allows some CPUs to go into dyntick-idle
|
|
mode during the locktorture test.
|
|
|
|
locktorture.shutdown_secs= [KNL]
|
|
Set time (s) after boot system shutdown. This
|
|
is useful for hands-off automated testing.
|
|
|
|
locktorture.stat_interval= [KNL]
|
|
Time (s) between statistics printk()s.
|
|
|
|
locktorture.stutter= [KNL]
|
|
Time (s) to stutter testing, for example,
|
|
specifying five seconds causes the test to run for
|
|
five seconds, wait for five seconds, and so on.
|
|
This tests the locking primitive's ability to
|
|
transition abruptly to and from idle.
|
|
|
|
locktorture.torture_type= [KNL]
|
|
Specify the locking implementation to test.
|
|
|
|
locktorture.verbose= [KNL]
|
|
Enable additional printk() statements.
|
|
|
|
logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
|
|
Format: <irq>
|
|
|
|
loglevel= All Kernel Messages with a loglevel smaller than the
|
|
console loglevel will be printed to the console. It can
|
|
also be changed with klogd or other programs. The
|
|
loglevels are defined as follows:
|
|
|
|
0 (KERN_EMERG) system is unusable
|
|
1 (KERN_ALERT) action must be taken immediately
|
|
2 (KERN_CRIT) critical conditions
|
|
3 (KERN_ERR) error conditions
|
|
4 (KERN_WARNING) warning conditions
|
|
5 (KERN_NOTICE) normal but significant condition
|
|
6 (KERN_INFO) informational
|
|
7 (KERN_DEBUG) debug-level messages
|
|
|
|
log_buf_len=n[KMG] Sets the size of the printk ring buffer,
|
|
in bytes. n must be a power of two and greater
|
|
than the minimal size. The minimal size is defined
|
|
by LOG_BUF_SHIFT kernel config parameter. There is
|
|
also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
|
|
that allows to increase the default size depending on
|
|
the number of CPUs. See init/Kconfig for more details.
|
|
|
|
logo.nologo [FB] Disables display of the built-in Linux logo.
|
|
This may be used to provide more screen space for
|
|
kernel log messages and is useful when debugging
|
|
kernel boot problems.
|
|
|
|
lp=0 [LP] Specify parallel ports to use, e.g,
|
|
lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
|
|
lp=reset first parallel port). 'lp=0' disables the
|
|
lp=auto printer driver. 'lp=reset' (which can be
|
|
specified in addition to the ports) causes
|
|
attached printers to be reset. Using
|
|
lp=port1,port2,... specifies the parallel ports
|
|
to associate lp devices with, starting with
|
|
lp0. A port specification may be 'none' to skip
|
|
that lp device, or a parport name such as
|
|
'parport0'. Specifying 'lp=auto' instead of a
|
|
port specification list means that device IDs
|
|
from each port should be examined, to see if
|
|
an IEEE 1284-compliant printer is attached; if
|
|
so, the driver will manage that printer.
|
|
See also header of drivers/char/lp.c.
|
|
|
|
lpj=n [KNL]
|
|
Sets loops_per_jiffy to given constant, thus avoiding
|
|
time-consuming boot-time autodetection (up to 250 ms per
|
|
CPU). 0 enables autodetection (default). To determine
|
|
the correct value for your kernel, boot with normal
|
|
autodetection and see what value is printed. Note that
|
|
on SMP systems the preset will be applied to all CPUs,
|
|
which is likely to cause problems if your CPUs need
|
|
significantly divergent settings. An incorrect value
|
|
will cause delays in the kernel to be wrong, leading to
|
|
unpredictable I/O errors and other breakage. Although
|
|
unlikely, in the extreme case this might damage your
|
|
hardware.
|
|
|
|
ltpc= [NET]
|
|
Format: <io>,<irq>,<dma>
|
|
|
|
lsm.debug [SECURITY] Enable LSM initialization debugging output.
|
|
|
|
lsm=lsm1,...,lsmN
|
|
[SECURITY] Choose order of LSM initialization. This
|
|
overrides CONFIG_LSM, and the "security=" parameter.
|
|
|
|
machvec= [IA-64] Force the use of a particular machine-vector
|
|
(machvec) in a generic kernel.
|
|
Example: machvec=hpzx1
|
|
|
|
machtype= [Loongson] Share the same kernel image file between
|
|
different yeeloong laptops.
|
|
Example: machtype=lemote-yeeloong-2f-7inch
|
|
|
|
max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
|
|
than or equal to this physical address is ignored.
|
|
|
|
maxcpus= [SMP] Maximum number of processors that an SMP kernel
|
|
will bring up during bootup. maxcpus=n : n >= 0 limits
|
|
the kernel to bring up 'n' processors. Surely after
|
|
bootup you can bring up the other plugged cpu by executing
|
|
"echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
|
|
only takes effect during system bootup.
|
|
While n=0 is a special case, it is equivalent to "nosmp",
|
|
which also disables the IO APIC.
|
|
|
|
max_loop= [LOOP] The number of loop block devices that get
|
|
(loop.max_loop) unconditionally pre-created at init time. The default
|
|
number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
|
|
of statically allocating a predefined number, loop
|
|
devices can be requested on-demand with the
|
|
/dev/loop-control interface.
|
|
|
|
mce [X86-32] Machine Check Exception
|
|
|
|
mce=option [X86-64] See Documentation/x86/x86_64/boot-options.rst
|
|
|
|
md= [HW] RAID subsystems devices and level
|
|
See Documentation/admin-guide/md.rst.
|
|
|
|
mdacon= [MDA]
|
|
Format: <first>,<last>
|
|
Specifies range of consoles to be captured by the MDA.
|
|
|
|
mds= [X86,INTEL]
|
|
Control mitigation for the Micro-architectural Data
|
|
Sampling (MDS) vulnerability.
|
|
|
|
Certain CPUs are vulnerable to an exploit against CPU
|
|
internal buffers which can forward information to a
|
|
disclosure gadget under certain conditions.
|
|
|
|
In vulnerable processors, the speculatively
|
|
forwarded data can be used in a cache side channel
|
|
attack, to access data to which the attacker does
|
|
not have direct access.
|
|
|
|
This parameter controls the MDS mitigation. The
|
|
options are:
|
|
|
|
full - Enable MDS mitigation on vulnerable CPUs
|
|
full,nosmt - Enable MDS mitigation and disable
|
|
SMT on vulnerable CPUs
|
|
off - Unconditionally disable MDS mitigation
|
|
|
|
On TAA-affected machines, mds=off can be prevented by
|
|
an active TAA mitigation as both vulnerabilities are
|
|
mitigated with the same mechanism so in order to disable
|
|
this mitigation, you need to specify tsx_async_abort=off
|
|
too.
|
|
|
|
Not specifying this option is equivalent to
|
|
mds=full.
|
|
|
|
For details see: Documentation/admin-guide/hw-vuln/mds.rst
|
|
|
|
mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
|
|
Amount of memory to be used in cases as follows:
|
|
|
|
1 for test;
|
|
2 when the kernel is not able to see the whole system memory;
|
|
3 memory that lies after 'mem=' boundary is excluded from
|
|
the hypervisor, then assigned to KVM guests.
|
|
|
|
[X86] Work as limiting max address. Use together
|
|
with memmap= to avoid physical address space collisions.
|
|
Without memmap= PCI devices could be placed at addresses
|
|
belonging to unused RAM.
|
|
|
|
Note that this only takes effects during boot time since
|
|
in above case 3, memory may need be hot added after boot
|
|
if system memory of hypervisor is not sufficient.
|
|
|
|
mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
|
|
memory.
|
|
|
|
memchunk=nn[KMG]
|
|
[KNL,SH] Allow user to override the default size for
|
|
per-device physically contiguous DMA buffers.
|
|
|
|
memhp_default_state=online/offline
|
|
[KNL] Set the initial state for the memory hotplug
|
|
onlining policy. If not specified, the default value is
|
|
set according to the
|
|
CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
|
|
option.
|
|
See Documentation/admin-guide/mm/memory-hotplug.rst.
|
|
|
|
memmap=exactmap [KNL,X86] Enable setting of an exact
|
|
E820 memory map, as specified by the user.
|
|
Such memmap=exactmap lines can be constructed based on
|
|
BIOS output or other requirements. See the memmap=nn@ss
|
|
option description.
|
|
|
|
memmap=nn[KMG]@ss[KMG]
|
|
[KNL, X86, MIPS, XTENSA] Force usage of a specific region of memory.
|
|
Region of memory to be used is from ss to ss+nn.
|
|
If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
|
|
which limits max address to nn[KMG].
|
|
Multiple different regions can be specified,
|
|
comma delimited.
|
|
Example:
|
|
memmap=100M@2G,100M#3G,1G!1024G
|
|
|
|
memmap=nn[KMG]#ss[KMG]
|
|
[KNL,ACPI] Mark specific memory as ACPI data.
|
|
Region of memory to be marked is from ss to ss+nn.
|
|
|
|
memmap=nn[KMG]$ss[KMG]
|
|
[KNL,ACPI] Mark specific memory as reserved.
|
|
Region of memory to be reserved is from ss to ss+nn.
|
|
Example: Exclude memory from 0x18690000-0x1869ffff
|
|
memmap=64K$0x18690000
|
|
or
|
|
memmap=0x10000$0x18690000
|
|
Some bootloaders may need an escape character before '$',
|
|
like Grub2, otherwise '$' and the following number
|
|
will be eaten.
|
|
|
|
memmap=nn[KMG]!ss[KMG]
|
|
[KNL,X86] Mark specific memory as protected.
|
|
Region of memory to be used, from ss to ss+nn.
|
|
The memory region may be marked as e820 type 12 (0xc)
|
|
and is NVDIMM or ADR memory.
|
|
|
|
memmap=<size>%<offset>-<oldtype>+<newtype>
|
|
[KNL,ACPI] Convert memory within the specified region
|
|
from <oldtype> to <newtype>. If "-<oldtype>" is left
|
|
out, the whole region will be marked as <newtype>,
|
|
even if previously unavailable. If "+<newtype>" is left
|
|
out, matching memory will be removed. Types are
|
|
specified as e820 types, e.g., 1 = RAM, 2 = reserved,
|
|
3 = ACPI, 12 = PRAM.
|
|
|
|
memory_corruption_check=0/1 [X86]
|
|
Some BIOSes seem to corrupt the first 64k of
|
|
memory when doing things like suspend/resume.
|
|
Setting this option will scan the memory
|
|
looking for corruption. Enabling this will
|
|
both detect corruption and prevent the kernel
|
|
from using the memory being corrupted.
|
|
However, its intended as a diagnostic tool; if
|
|
repeatable BIOS-originated corruption always
|
|
affects the same memory, you can use memmap=
|
|
to prevent the kernel from using that memory.
|
|
|
|
memory_corruption_check_size=size [X86]
|
|
By default it checks for corruption in the low
|
|
64k, making this memory unavailable for normal
|
|
use. Use this parameter to scan for
|
|
corruption in more or less memory.
|
|
|
|
memory_corruption_check_period=seconds [X86]
|
|
By default it checks for corruption every 60
|
|
seconds. Use this parameter to check at some
|
|
other rate. 0 disables periodic checking.
|
|
|
|
memtest= [KNL,X86,ARM,PPC] Enable memtest
|
|
Format: <integer>
|
|
default : 0 <disable>
|
|
Specifies the number of memtest passes to be
|
|
performed. Each pass selects another test
|
|
pattern from a given set of patterns. Memtest
|
|
fills the memory with this pattern, validates
|
|
memory contents and reserves bad memory
|
|
regions that are detected.
|
|
|
|
mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control
|
|
Valid arguments: on, off
|
|
Default (depends on kernel configuration option):
|
|
on (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y)
|
|
off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n)
|
|
mem_encrypt=on: Activate SME
|
|
mem_encrypt=off: Do not activate SME
|
|
|
|
Refer to Documentation/virt/kvm/amd-memory-encryption.rst
|
|
for details on when memory encryption can be activated.
|
|
|
|
mem_sleep_default= [SUSPEND] Default system suspend mode:
|
|
s2idle - Suspend-To-Idle
|
|
shallow - Power-On Suspend or equivalent (if supported)
|
|
deep - Suspend-To-RAM or equivalent (if supported)
|
|
See Documentation/admin-guide/pm/sleep-states.rst.
|
|
|
|
meye.*= [HW] Set MotionEye Camera parameters
|
|
See Documentation/admin-guide/media/meye.rst.
|
|
|
|
mfgpt_irq= [IA-32] Specify the IRQ to use for the
|
|
Multi-Function General Purpose Timers on AMD Geode
|
|
platforms.
|
|
|
|
mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
|
|
the BIOS has incorrectly applied a workaround. TinyBIOS
|
|
version 0.98 is known to be affected, 0.99 fixes the
|
|
problem by letting the user disable the workaround.
|
|
|
|
mga= [HW,DRM]
|
|
|
|
min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
|
|
physical address is ignored.
|
|
|
|
mini2440= [ARM,HW,KNL]
|
|
Format:[0..2][b][c][t]
|
|
Default: "0tb"
|
|
MINI2440 configuration specification:
|
|
0 - The attached screen is the 3.5" TFT
|
|
1 - The attached screen is the 7" TFT
|
|
2 - The VGA Shield is attached (1024x768)
|
|
Leaving out the screen size parameter will not load
|
|
the TFT driver, and the framebuffer will be left
|
|
unconfigured.
|
|
b - Enable backlight. The TFT backlight pin will be
|
|
linked to the kernel VESA blanking code and a GPIO
|
|
LED. This parameter is not necessary when using the
|
|
VGA shield.
|
|
c - Enable the s3c camera interface.
|
|
t - Reserved for enabling touchscreen support. The
|
|
touchscreen support is not enabled in the mainstream
|
|
kernel as of 2.6.30, a preliminary port can be found
|
|
in the "bleeding edge" mini2440 support kernel at
|
|
https://repo.or.cz/w/linux-2.6/mini2440.git
|
|
|
|
mitigations=
|
|
[X86,PPC,S390,ARM64] Control optional mitigations for
|
|
CPU vulnerabilities. This is a set of curated,
|
|
arch-independent options, each of which is an
|
|
aggregation of existing arch-specific options.
|
|
|
|
off
|
|
Disable all optional CPU mitigations. This
|
|
improves system performance, but it may also
|
|
expose users to several CPU vulnerabilities.
|
|
Equivalent to: nopti [X86,PPC]
|
|
kpti=0 [ARM64]
|
|
nospectre_v1 [X86,PPC]
|
|
nobp=0 [S390]
|
|
nospectre_v2 [X86,PPC,S390,ARM64]
|
|
spectre_v2_user=off [X86]
|
|
spec_store_bypass_disable=off [X86,PPC]
|
|
ssbd=force-off [ARM64]
|
|
l1tf=off [X86]
|
|
mds=off [X86]
|
|
tsx_async_abort=off [X86]
|
|
kvm.nx_huge_pages=off [X86]
|
|
no_entry_flush [PPC]
|
|
no_uaccess_flush [PPC]
|
|
|
|
Exceptions:
|
|
This does not have any effect on
|
|
kvm.nx_huge_pages when
|
|
kvm.nx_huge_pages=force.
|
|
|
|
auto (default)
|
|
Mitigate all CPU vulnerabilities, but leave SMT
|
|
enabled, even if it's vulnerable. This is for
|
|
users who don't want to be surprised by SMT
|
|
getting disabled across kernel upgrades, or who
|
|
have other ways of avoiding SMT-based attacks.
|
|
Equivalent to: (default behavior)
|
|
|
|
auto,nosmt
|
|
Mitigate all CPU vulnerabilities, disabling SMT
|
|
if needed. This is for users who always want to
|
|
be fully mitigated, even if it means losing SMT.
|
|
Equivalent to: l1tf=flush,nosmt [X86]
|
|
mds=full,nosmt [X86]
|
|
tsx_async_abort=full,nosmt [X86]
|
|
|
|
mminit_loglevel=
|
|
[KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
|
|
parameter allows control of the logging verbosity for
|
|
the additional memory initialisation checks. A value
|
|
of 0 disables mminit logging and a level of 4 will
|
|
log everything. Information is printed at KERN_DEBUG
|
|
so loglevel=8 may also need to be specified.
|
|
|
|
module.sig_enforce
|
|
[KNL] When CONFIG_MODULE_SIG is set, this means that
|
|
modules without (valid) signatures will fail to load.
|
|
Note that if CONFIG_MODULE_SIG_FORCE is set, that
|
|
is always true, so this option does nothing.
|
|
|
|
module_blacklist= [KNL] Do not load a comma-separated list of
|
|
modules. Useful for debugging problem modules.
|
|
|
|
mousedev.tap_time=
|
|
[MOUSE] Maximum time between finger touching and
|
|
leaving touchpad surface for touch to be considered
|
|
a tap and be reported as a left button click (for
|
|
touchpads working in absolute mode only).
|
|
Format: <msecs>
|
|
mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
|
|
reporting absolute coordinates, such as tablets
|
|
mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
|
|
reporting absolute coordinates, such as tablets
|
|
|
|
movablecore= [KNL,X86,IA-64,PPC]
|
|
Format: nn[KMGTPE] | nn%
|
|
This parameter is the complement to kernelcore=, it
|
|
specifies the amount of memory used for migratable
|
|
allocations. If both kernelcore and movablecore is
|
|
specified, then kernelcore will be at *least* the
|
|
specified value but may be more. If movablecore on its
|
|
own is specified, the administrator must be careful
|
|
that the amount of memory usable for all allocations
|
|
is not too small.
|
|
|
|
movable_node [KNL] Boot-time switch to make hotplugable memory
|
|
NUMA nodes to be movable. This means that the memory
|
|
of such nodes will be usable only for movable
|
|
allocations which rules out almost all kernel
|
|
allocations. Use with caution!
|
|
|
|
MTD_Partition= [MTD]
|
|
Format: <name>,<region-number>,<size>,<offset>
|
|
|
|
MTD_Region= [MTD] Format:
|
|
<name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
|
|
|
|
mtdparts= [MTD]
|
|
See drivers/mtd/parsers/cmdlinepart.c
|
|
|
|
multitce=off [PPC] This parameter disables the use of the pSeries
|
|
firmware feature for updating multiple TCE entries
|
|
at a time.
|
|
|
|
onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
|
|
|
|
Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
|
|
|
|
boundary - index of last SLC block on Flex-OneNAND.
|
|
The remaining blocks are configured as MLC blocks.
|
|
lock - Configure if Flex-OneNAND boundary should be locked.
|
|
Once locked, the boundary cannot be changed.
|
|
1 indicates lock status, 0 indicates unlock status.
|
|
|
|
mtdset= [ARM]
|
|
ARM/S3C2412 JIVE boot control
|
|
|
|
See arch/arm/mach-s3c/mach-jive.c
|
|
|
|
mtouchusb.raw_coordinates=
|
|
[HW] Make the MicroTouch USB driver use raw coordinates
|
|
('y', default) or cooked coordinates ('n')
|
|
|
|
mtrr_chunk_size=nn[KMG] [X86]
|
|
used for mtrr cleanup. It is largest continuous chunk
|
|
that could hold holes aka. UC entries.
|
|
|
|
mtrr_gran_size=nn[KMG] [X86]
|
|
Used for mtrr cleanup. It is granularity of mtrr block.
|
|
Default is 1.
|
|
Large value could prevent small alignment from
|
|
using up MTRRs.
|
|
|
|
mtrr_spare_reg_nr=n [X86]
|
|
Format: <integer>
|
|
Range: 0,7 : spare reg number
|
|
Default : 1
|
|
Used for mtrr cleanup. It is spare mtrr entries number.
|
|
Set to 2 or more if your graphical card needs more.
|
|
|
|
n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
|
|
|
|
netdev= [NET] Network devices parameters
|
|
Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
|
|
Note that mem_start is often overloaded to mean
|
|
something different and driver-specific.
|
|
This usage is only documented in each driver source
|
|
file if at all.
|
|
|
|
nf_conntrack.acct=
|
|
[NETFILTER] Enable connection tracking flow accounting
|
|
0 to disable accounting
|
|
1 to enable accounting
|
|
Default value is 0.
|
|
|
|
nfsaddrs= [NFS] Deprecated. Use ip= instead.
|
|
See Documentation/admin-guide/nfs/nfsroot.rst.
|
|
|
|
nfsroot= [NFS] nfs root filesystem for disk-less boxes.
|
|
See Documentation/admin-guide/nfs/nfsroot.rst.
|
|
|
|
nfsrootdebug [NFS] enable nfsroot debugging messages.
|
|
See Documentation/admin-guide/nfs/nfsroot.rst.
|
|
|
|
nfs.callback_nr_threads=
|
|
[NFSv4] set the total number of threads that the
|
|
NFS client will assign to service NFSv4 callback
|
|
requests.
|
|
|
|
nfs.callback_tcpport=
|
|
[NFS] set the TCP port on which the NFSv4 callback
|
|
channel should listen.
|
|
|
|
nfs.cache_getent=
|
|
[NFS] sets the pathname to the program which is used
|
|
to update the NFS client cache entries.
|
|
|
|
nfs.cache_getent_timeout=
|
|
[NFS] sets the timeout after which an attempt to
|
|
update a cache entry is deemed to have failed.
|
|
|
|
nfs.idmap_cache_timeout=
|
|
[NFS] set the maximum lifetime for idmapper cache
|
|
entries.
|
|
|
|
nfs.enable_ino64=
|
|
[NFS] enable 64-bit inode numbers.
|
|
If zero, the NFS client will fake up a 32-bit inode
|
|
number for the readdir() and stat() syscalls instead
|
|
of returning the full 64-bit number.
|
|
The default is to return 64-bit inode numbers.
|
|
|
|
nfs.max_session_cb_slots=
|
|
[NFSv4.1] Sets the maximum number of session
|
|
slots the client will assign to the callback
|
|
channel. This determines the maximum number of
|
|
callbacks the client will process in parallel for
|
|
a particular server.
|
|
|
|
nfs.max_session_slots=
|
|
[NFSv4.1] Sets the maximum number of session slots
|
|
the client will attempt to negotiate with the server.
|
|
This limits the number of simultaneous RPC requests
|
|
that the client can send to the NFSv4.1 server.
|
|
Note that there is little point in setting this
|
|
value higher than the max_tcp_slot_table_limit.
|
|
|
|
nfs.nfs4_disable_idmapping=
|
|
[NFSv4] When set to the default of '1', this option
|
|
ensures that both the RPC level authentication
|
|
scheme and the NFS level operations agree to use
|
|
numeric uids/gids if the mount is using the
|
|
'sec=sys' security flavour. In effect it is
|
|
disabling idmapping, which can make migration from
|
|
legacy NFSv2/v3 systems to NFSv4 easier.
|
|
Servers that do not support this mode of operation
|
|
will be autodetected by the client, and it will fall
|
|
back to using the idmapper.
|
|
To turn off this behaviour, set the value to '0'.
|
|
nfs.nfs4_unique_id=
|
|
[NFS4] Specify an additional fixed unique ident-
|
|
ification string that NFSv4 clients can insert into
|
|
their nfs_client_id4 string. This is typically a
|
|
UUID that is generated at system install time.
|
|
|
|
nfs.send_implementation_id =
|
|
[NFSv4.1] Send client implementation identification
|
|
information in exchange_id requests.
|
|
If zero, no implementation identification information
|
|
will be sent.
|
|
The default is to send the implementation identification
|
|
information.
|
|
|
|
nfs.recover_lost_locks =
|
|
[NFSv4] Attempt to recover locks that were lost due
|
|
to a lease timeout on the server. Please note that
|
|
doing this risks data corruption, since there are
|
|
no guarantees that the file will remain unchanged
|
|
after the locks are lost.
|
|
If you want to enable the kernel legacy behaviour of
|
|
attempting to recover these locks, then set this
|
|
parameter to '1'.
|
|
The default parameter value of '0' causes the kernel
|
|
not to attempt recovery of lost locks.
|
|
|
|
nfs4.layoutstats_timer =
|
|
[NFSv4.2] Change the rate at which the kernel sends
|
|
layoutstats to the pNFS metadata server.
|
|
|
|
Setting this to value to 0 causes the kernel to use
|
|
whatever value is the default set by the layout
|
|
driver. A non-zero value sets the minimum interval
|
|
in seconds between layoutstats transmissions.
|
|
|
|
nfsd.nfs4_disable_idmapping=
|
|
[NFSv4] When set to the default of '1', the NFSv4
|
|
server will return only numeric uids and gids to
|
|
clients using auth_sys, and will accept numeric uids
|
|
and gids from such clients. This is intended to ease
|
|
migration from NFSv2/v3.
|
|
|
|
nmi_backtrace.backtrace_idle [KNL]
|
|
Dump stacks even of idle CPUs in response to an
|
|
NMI stack-backtrace request.
|
|
|
|
nmi_debug= [KNL,SH] Specify one or more actions to take
|
|
when a NMI is triggered.
|
|
Format: [state][,regs][,debounce][,die]
|
|
|
|
nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
|
|
Format: [panic,][nopanic,][num]
|
|
Valid num: 0 or 1
|
|
0 - turn hardlockup detector in nmi_watchdog off
|
|
1 - turn hardlockup detector in nmi_watchdog on
|
|
When panic is specified, panic when an NMI watchdog
|
|
timeout occurs (or 'nopanic' to not panic on an NMI
|
|
watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set)
|
|
To disable both hard and soft lockup detectors,
|
|
please see 'nowatchdog'.
|
|
This is useful when you use a panic=... timeout and
|
|
need the box quickly up again.
|
|
|
|
These settings can be accessed at runtime via
|
|
the nmi_watchdog and hardlockup_panic sysctls.
|
|
|
|
netpoll.carrier_timeout=
|
|
[NET] Specifies amount of time (in seconds) that
|
|
netpoll should wait for a carrier. By default netpoll
|
|
waits 4 seconds.
|
|
|
|
no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
|
|
emulation library even if a 387 maths coprocessor
|
|
is present.
|
|
|
|
no5lvl [X86-64] Disable 5-level paging mode. Forces
|
|
kernel to use 4-level paging instead.
|
|
|
|
nofsgsbase [X86] Disables FSGSBASE instructions.
|
|
|
|
no_console_suspend
|
|
[HW] Never suspend the console
|
|
Disable suspending of consoles during suspend and
|
|
hibernate operations. Once disabled, debugging
|
|
messages can reach various consoles while the rest
|
|
of the system is being put to sleep (ie, while
|
|
debugging driver suspend/resume hooks). This may
|
|
not work reliably with all consoles, but is known
|
|
to work with serial and VGA consoles.
|
|
To facilitate more flexible debugging, we also add
|
|
console_suspend, a printk module parameter to control
|
|
it. Users could use console_suspend (usually
|
|
/sys/module/printk/parameters/console_suspend) to
|
|
turn on/off it dynamically.
|
|
|
|
novmcoredd [KNL,KDUMP]
|
|
Disable device dump. Device dump allows drivers to
|
|
append dump data to vmcore so you can collect driver
|
|
specified debug info. Drivers can append the data
|
|
without any limit and this data is stored in memory,
|
|
so this may cause significant memory stress. Disabling
|
|
device dump can help save memory but the driver debug
|
|
data will be no longer available. This parameter
|
|
is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP
|
|
is set.
|
|
|
|
noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
|
|
caches in the slab allocator. Saves per-node memory,
|
|
but will impact performance.
|
|
|
|
noalign [KNL,ARM]
|
|
|
|
noaltinstr [S390] Disables alternative instructions patching
|
|
(CPU alternatives feature).
|
|
|
|
noapic [SMP,APIC] Tells the kernel to not make use of any
|
|
IOAPICs that may be present in the system.
|
|
|
|
noautogroup Disable scheduler automatic task group creation.
|
|
|
|
nobats [PPC] Do not use BATs for mapping kernel lowmem
|
|
on "Classic" PPC cores.
|
|
|
|
nocache [ARM]
|
|
|
|
noclflush [BUGS=X86] Don't use the CLFLUSH instruction
|
|
|
|
nodelayacct [KNL] Disable per-task delay accounting
|
|
|
|
nodsp [SH] Disable hardware DSP at boot time.
|
|
|
|
noefi Disable EFI runtime services support.
|
|
|
|
no_entry_flush [PPC] Don't flush the L1-D cache when entering the kernel.
|
|
|
|
noexec [IA-64]
|
|
|
|
noexec [X86]
|
|
On X86-32 available only on PAE configured kernels.
|
|
noexec=on: enable non-executable mappings (default)
|
|
noexec=off: disable non-executable mappings
|
|
|
|
nosmap [X86,PPC]
|
|
Disable SMAP (Supervisor Mode Access Prevention)
|
|
even if it is supported by processor.
|
|
|
|
nosmep [X86,PPC]
|
|
Disable SMEP (Supervisor Mode Execution Prevention)
|
|
even if it is supported by processor.
|
|
|
|
noexec32 [X86-64]
|
|
This affects only 32-bit executables.
|
|
noexec32=on: enable non-executable mappings (default)
|
|
read doesn't imply executable mappings
|
|
noexec32=off: disable non-executable mappings
|
|
read implies executable mappings
|
|
|
|
nofpu [MIPS,SH] Disable hardware FPU at boot time.
|
|
|
|
nofxsr [BUGS=X86-32] Disables x86 floating point extended
|
|
register save and restore. The kernel will only save
|
|
legacy floating-point registers on task switch.
|
|
|
|
nohugeiomap [KNL,X86,PPC,ARM64] Disable kernel huge I/O mappings.
|
|
|
|
nosmt [KNL,S390] Disable symmetric multithreading (SMT).
|
|
Equivalent to smt=1.
|
|
|
|
[KNL,X86] Disable symmetric multithreading (SMT).
|
|
nosmt=force: Force disable SMT, cannot be undone
|
|
via the sysfs control file.
|
|
|
|
nospectre_v1 [X86,PPC] Disable mitigations for Spectre Variant 1
|
|
(bounds check bypass). With this option data leaks are
|
|
possible in the system.
|
|
|
|
nospectre_v2 [X86,PPC_FSL_BOOK3E,ARM64] Disable all mitigations for
|
|
the Spectre variant 2 (indirect branch prediction)
|
|
vulnerability. System may allow data leaks with this
|
|
option.
|
|
|
|
nospec_store_bypass_disable
|
|
[HW] Disable all mitigations for the Speculative Store Bypass vulnerability
|
|
|
|
no_uaccess_flush
|
|
[PPC] Don't flush the L1-D cache after accessing user data.
|
|
|
|
noxsave [BUGS=X86] Disables x86 extended register state save
|
|
and restore using xsave. The kernel will fallback to
|
|
enabling legacy floating-point and sse state.
|
|
|
|
noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
|
|
register states. The kernel will fall back to use
|
|
xsave to save the states. By using this parameter,
|
|
performance of saving the states is degraded because
|
|
xsave doesn't support modified optimization while
|
|
xsaveopt supports it on xsaveopt enabled systems.
|
|
|
|
noxsaves [X86] Disables xsaves and xrstors used in saving and
|
|
restoring x86 extended register state in compacted
|
|
form of xsave area. The kernel will fall back to use
|
|
xsaveopt and xrstor to save and restore the states
|
|
in standard form of xsave area. By using this
|
|
parameter, xsave area per process might occupy more
|
|
memory on xsaves enabled systems.
|
|
|
|
nohlt [ARM,ARM64,MICROBLAZE,SH] Forces the kernel to busy wait
|
|
in do_idle() and not use the arch_cpu_idle()
|
|
implementation; requires CONFIG_GENERIC_IDLE_POLL_SETUP
|
|
to be effective. This is useful on platforms where the
|
|
sleep(SH) or wfi(ARM,ARM64) instructions do not work
|
|
correctly or when doing power measurements to evalute
|
|
the impact of the sleep instructions. This is also
|
|
useful when using JTAG debugger.
|
|
|
|
no_file_caps Tells the kernel not to honor file capabilities. The
|
|
only way then for a file to be executed with privilege
|
|
is to be setuid root or executed by root.
|
|
|
|
nohalt [IA-64] Tells the kernel not to use the power saving
|
|
function PAL_HALT_LIGHT when idle. This increases
|
|
power-consumption. On the positive side, it reduces
|
|
interrupt wake-up latency, which may improve performance
|
|
in certain environments such as networked servers or
|
|
real-time systems.
|
|
|
|
no_hash_pointers
|
|
Force pointers printed to the console or buffers to be
|
|
unhashed. By default, when a pointer is printed via %p
|
|
format string, that pointer is "hashed", i.e. obscured
|
|
by hashing the pointer value. This is a security feature
|
|
that hides actual kernel addresses from unprivileged
|
|
users, but it also makes debugging the kernel more
|
|
difficult since unequal pointers can no longer be
|
|
compared. However, if this command-line option is
|
|
specified, then all normal pointers will have their true
|
|
value printed. Pointers printed via %pK may still be
|
|
hashed. This option should only be specified when
|
|
debugging the kernel. Please do not use on production
|
|
kernels.
|
|
|
|
nohibernate [HIBERNATION] Disable hibernation and resume.
|
|
|
|
nohz= [KNL] Boottime enable/disable dynamic ticks
|
|
Valid arguments: on, off
|
|
Default: on
|
|
|
|
nohz_full= [KNL,BOOT,SMP,ISOL]
|
|
The argument is a cpu list, as described above.
|
|
In kernels built with CONFIG_NO_HZ_FULL=y, set
|
|
the specified list of CPUs whose tick will be stopped
|
|
whenever possible. The boot CPU will be forced outside
|
|
the range to maintain the timekeeping. Any CPUs
|
|
in this list will have their RCU callbacks offloaded,
|
|
just as if they had also been called out in the
|
|
rcu_nocbs= boot parameter.
|
|
|
|
noiotrap [SH] Disables trapped I/O port accesses.
|
|
|
|
noirqdebug [X86-32] Disables the code which attempts to detect and
|
|
disable unhandled interrupt sources.
|
|
|
|
no_timer_check [X86,APIC] Disables the code which tests for
|
|
broken timer IRQ sources.
|
|
|
|
noisapnp [ISAPNP] Disables ISA PnP code.
|
|
|
|
noinitrd [RAM] Tells the kernel not to load any configured
|
|
initial RAM disk.
|
|
|
|
nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
|
|
remapping.
|
|
[Deprecated - use intremap=off]
|
|
|
|
nointroute [IA-64]
|
|
|
|
noinvpcid [X86] Disable the INVPCID cpu feature.
|
|
|
|
nojitter [IA-64] Disables jitter checking for ITC timers.
|
|
|
|
no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
|
|
|
|
no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
|
|
fault handling.
|
|
|
|
no-vmw-sched-clock
|
|
[X86,PV_OPS] Disable paravirtualized VMware scheduler
|
|
clock and use the default one.
|
|
|
|
no-steal-acc [X86,PV_OPS,ARM64] Disable paravirtualized steal time
|
|
accounting. steal time is computed, but won't
|
|
influence scheduler behaviour
|
|
|
|
nolapic [X86-32,APIC] Do not enable or use the local APIC.
|
|
|
|
nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
|
|
|
|
noltlbs [PPC] Do not use large page/tlb entries for kernel
|
|
lowmem mapping on PPC40x and PPC8xx
|
|
|
|
nomca [IA-64] Disable machine check abort handling
|
|
|
|
nomce [X86-32] Disable Machine Check Exception
|
|
|
|
nomfgpt [X86-32] Disable Multi-Function General Purpose
|
|
Timer usage (for AMD Geode machines).
|
|
|
|
nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
|
|
shutdown the other cpus. Instead use the REBOOT_VECTOR
|
|
irq.
|
|
|
|
nomodule Disable module load
|
|
|
|
nopat [X86] Disable PAT (page attribute table extension of
|
|
pagetables) support.
|
|
|
|
nopcid [X86-64] Disable the PCID cpu feature.
|
|
|
|
norandmaps Don't use address space randomization. Equivalent to
|
|
echo 0 > /proc/sys/kernel/randomize_va_space
|
|
|
|
noreplace-smp [X86-32,SMP] Don't replace SMP instructions
|
|
with UP alternatives
|
|
|
|
nordrand [X86] Disable kernel use of the RDRAND and
|
|
RDSEED instructions even if they are supported
|
|
by the processor. RDRAND and RDSEED are still
|
|
available to user space applications.
|
|
|
|
noresume [SWSUSP] Disables resume and restores original swap
|
|
space.
|
|
|
|
no-scroll [VGA] Disables scrollback.
|
|
This is required for the Braillex ib80-piezo Braille
|
|
reader made by F.H. Papenmeier (Germany).
|
|
|
|
nosbagart [IA-64]
|
|
|
|
nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
|
|
|
|
nosgx [X86-64,SGX] Disables Intel SGX kernel support.
|
|
|
|
nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
|
|
and disable the IO APIC. legacy for "maxcpus=0".
|
|
|
|
nosoftlockup [KNL] Disable the soft-lockup detector.
|
|
|
|
nosync [HW,M68K] Disables sync negotiation for all devices.
|
|
|
|
nowatchdog [KNL] Disable both lockup detectors, i.e.
|
|
soft-lockup and NMI watchdog (hard-lockup).
|
|
|
|
nowb [ARM]
|
|
|
|
nox2apic [X86-64,APIC] Do not enable x2APIC mode.
|
|
|
|
cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
|
|
CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
|
|
Some features depend on CPU0. Known dependencies are:
|
|
1. Resume from suspend/hibernate depends on CPU0.
|
|
Suspend/hibernate will fail if CPU0 is offline and you
|
|
need to online CPU0 before suspend/hibernate.
|
|
2. PIC interrupts also depend on CPU0. CPU0 can't be
|
|
removed if a PIC interrupt is detected.
|
|
It's said poweroff/reboot may depend on CPU0 on some
|
|
machines although I haven't seen such issues so far
|
|
after CPU0 is offline on a few tested machines.
|
|
If the dependencies are under your control, you can
|
|
turn on cpu0_hotplug.
|
|
|
|
nps_mtm_hs_ctr= [KNL,ARC]
|
|
This parameter sets the maximum duration, in
|
|
cycles, each HW thread of the CTOP can run
|
|
without interruptions, before HW switches it.
|
|
The actual maximum duration is 16 times this
|
|
parameter's value.
|
|
Format: integer between 1 and 255
|
|
Default: 255
|
|
|
|
nptcg= [IA-64] Override max number of concurrent global TLB
|
|
purges which is reported from either PAL_VM_SUMMARY or
|
|
SAL PALO.
|
|
|
|
nr_cpus= [SMP] Maximum number of processors that an SMP kernel
|
|
could support. nr_cpus=n : n >= 1 limits the kernel to
|
|
support 'n' processors. It could be larger than the
|
|
number of already plugged CPU during bootup, later in
|
|
runtime you can physically add extra cpu until it reaches
|
|
n. So during boot up some boot time memory for per-cpu
|
|
variables need be pre-allocated for later physical cpu
|
|
hot plugging.
|
|
|
|
nr_uarts= [SERIAL] maximum number of UARTs to be registered.
|
|
|
|
numa_balancing= [KNL,ARM64,PPC,RISCV,S390,X86] Enable or disable automatic
|
|
NUMA balancing.
|
|
Allowed values are enable and disable
|
|
|
|
numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
|
|
'node', 'default' can be specified
|
|
This can be set from sysctl after boot.
|
|
See Documentation/admin-guide/sysctl/vm.rst for details.
|
|
|
|
ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
|
|
See Documentation/core-api/debugging-via-ohci1394.rst for more
|
|
info.
|
|
|
|
olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
|
|
Rather than timing out after 20 ms if an EC
|
|
command is not properly ACKed, override the length
|
|
of the timeout. We have interrupts disabled while
|
|
waiting for the ACK, so if this is set too high
|
|
interrupts *may* be lost!
|
|
|
|
omap_mux= [OMAP] Override bootloader pin multiplexing.
|
|
Format: <mux_mode0.mode_name=value>...
|
|
For example, to override I2C bus2:
|
|
omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
|
|
|
|
oops=panic Always panic on oopses. Default is to just kill the
|
|
process, but there is a small probability of
|
|
deadlocking the machine.
|
|
This will also cause panics on machine check exceptions.
|
|
Useful together with panic=30 to trigger a reboot.
|
|
|
|
page_alloc.shuffle=
|
|
[KNL] Boolean flag to control whether the page allocator
|
|
should randomize its free lists. The randomization may
|
|
be automatically enabled if the kernel detects it is
|
|
running on a platform with a direct-mapped memory-side
|
|
cache, and this parameter can be used to
|
|
override/disable that behavior. The state of the flag
|
|
can be read from sysfs at:
|
|
/sys/module/page_alloc/parameters/shuffle.
|
|
|
|
page_owner= [KNL] Boot-time page_owner enabling option.
|
|
Storage of the information about who allocated
|
|
each page is disabled in default. With this switch,
|
|
we can turn it on.
|
|
on: enable the feature
|
|
|
|
page_poison= [KNL] Boot-time parameter changing the state of
|
|
poisoning on the buddy allocator, available with
|
|
CONFIG_PAGE_POISONING=y.
|
|
off: turn off poisoning (default)
|
|
on: turn on poisoning
|
|
|
|
panic= [KNL] Kernel behaviour on panic: delay <timeout>
|
|
timeout > 0: seconds before rebooting
|
|
timeout = 0: wait forever
|
|
timeout < 0: reboot immediately
|
|
Format: <timeout>
|
|
|
|
panic_print= Bitmask for printing system info when panic happens.
|
|
User can chose combination of the following bits:
|
|
bit 0: print all tasks info
|
|
bit 1: print system memory info
|
|
bit 2: print timer info
|
|
bit 3: print locks info if CONFIG_LOCKDEP is on
|
|
bit 4: print ftrace buffer
|
|
bit 5: print all printk messages in buffer
|
|
|
|
panic_on_taint= Bitmask for conditionally calling panic() in add_taint()
|
|
Format: <hex>[,nousertaint]
|
|
Hexadecimal bitmask representing the set of TAINT flags
|
|
that will cause the kernel to panic when add_taint() is
|
|
called with any of the flags in this set.
|
|
The optional switch "nousertaint" can be utilized to
|
|
prevent userspace forced crashes by writing to sysctl
|
|
/proc/sys/kernel/tainted any flagset matching with the
|
|
bitmask set on panic_on_taint.
|
|
See Documentation/admin-guide/tainted-kernels.rst for
|
|
extra details on the taint flags that users can pick
|
|
to compose the bitmask to assign to panic_on_taint.
|
|
|
|
panic_on_warn panic() instead of WARN(). Useful to cause kdump
|
|
on a WARN().
|
|
|
|
crash_kexec_post_notifiers
|
|
Run kdump after running panic-notifiers and dumping
|
|
kmsg. This only for the users who doubt kdump always
|
|
succeeds in any situation.
|
|
Note that this also increases risks of kdump failure,
|
|
because some panic notifiers can make the crashed
|
|
kernel more unstable.
|
|
|
|
parkbd.port= [HW] Parallel port number the keyboard adapter is
|
|
connected to, default is 0.
|
|
Format: <parport#>
|
|
parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
|
|
0 for XT, 1 for AT (default is AT).
|
|
Format: <mode>
|
|
|
|
parport= [HW,PPT] Specify parallel ports. 0 disables.
|
|
Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
|
|
Use 'auto' to force the driver to use any
|
|
IRQ/DMA settings detected (the default is to
|
|
ignore detected IRQ/DMA settings because of
|
|
possible conflicts). You can specify the base
|
|
address, IRQ, and DMA settings; IRQ and DMA
|
|
should be numbers, or 'auto' (for using detected
|
|
settings on that particular port), or 'nofifo'
|
|
(to avoid using a FIFO even if it is detected).
|
|
Parallel ports are assigned in the order they
|
|
are specified on the command line, starting
|
|
with parport0.
|
|
|
|
parport_init_mode= [HW,PPT]
|
|
Configure VIA parallel port to operate in
|
|
a specific mode. This is necessary on Pegasos
|
|
computer where firmware has no options for setting
|
|
up parallel port mode and sets it to spp.
|
|
Currently this function knows 686a and 8231 chips.
|
|
Format: [spp|ps2|epp|ecp|ecpepp]
|
|
|
|
pata_legacy.all= [HW,LIBATA]
|
|
Format: <int>
|
|
Set to non-zero to probe primary and secondary ISA
|
|
port ranges on PCI systems where no PCI PATA device
|
|
has been found at either range. Disabled by default.
|
|
|
|
pata_legacy.autospeed= [HW,LIBATA]
|
|
Format: <int>
|
|
Set to non-zero if a chip is present that snoops speed
|
|
changes. Disabled by default.
|
|
|
|
pata_legacy.ht6560a= [HW,LIBATA]
|
|
Format: <int>
|
|
Set to 1, 2, or 3 for HT 6560A on the primary channel,
|
|
the secondary channel, or both channels respectively.
|
|
Disabled by default.
|
|
|
|
pata_legacy.ht6560b= [HW,LIBATA]
|
|
Format: <int>
|
|
Set to 1, 2, or 3 for HT 6560B on the primary channel,
|
|
the secondary channel, or both channels respectively.
|
|
Disabled by default.
|
|
|
|
pata_legacy.iordy_mask= [HW,LIBATA]
|
|
Format: <int>
|
|
IORDY enable mask. Set individual bits to allow IORDY
|
|
for the respective channel. Bit 0 is for the first
|
|
legacy channel handled by this driver, bit 1 is for
|
|
the second channel, and so on. The sequence will often
|
|
correspond to the primary legacy channel, the secondary
|
|
legacy channel, and so on, but the handling of a PCI
|
|
bus and the use of other driver options may interfere
|
|
with the sequence. By default IORDY is allowed across
|
|
all channels.
|
|
|
|
pata_legacy.opti82c46x= [HW,LIBATA]
|
|
Format: <int>
|
|
Set to 1, 2, or 3 for Opti 82c611A on the primary
|
|
channel, the secondary channel, or both channels
|
|
respectively. Disabled by default.
|
|
|
|
pata_legacy.opti82c611a= [HW,LIBATA]
|
|
Format: <int>
|
|
Set to 1, 2, or 3 for Opti 82c465MV on the primary
|
|
channel, the secondary channel, or both channels
|
|
respectively. Disabled by default.
|
|
|
|
pata_legacy.pio_mask= [HW,LIBATA]
|
|
Format: <int>
|
|
PIO mode mask for autospeed devices. Set individual
|
|
bits to allow the use of the respective PIO modes.
|
|
Bit 0 is for mode 0, bit 1 is for mode 1, and so on.
|
|
All modes allowed by default.
|
|
|
|
pata_legacy.probe_all= [HW,LIBATA]
|
|
Format: <int>
|
|
Set to non-zero to probe tertiary and further ISA
|
|
port ranges on PCI systems. Disabled by default.
|
|
|
|
pata_legacy.probe_mask= [HW,LIBATA]
|
|
Format: <int>
|
|
Probe mask for legacy ISA PATA ports. Depending on
|
|
platform configuration and the use of other driver
|
|
options up to 6 legacy ports are supported: 0x1f0,
|
|
0x170, 0x1e8, 0x168, 0x1e0, 0x160, however probing
|
|
of individual ports can be disabled by setting the
|
|
corresponding bits in the mask to 1. Bit 0 is for
|
|
the first port in the list above (0x1f0), and so on.
|
|
By default all supported ports are probed.
|
|
|
|
pata_legacy.qdi= [HW,LIBATA]
|
|
Format: <int>
|
|
Set to non-zero to probe QDI controllers. By default
|
|
set to 1 if CONFIG_PATA_QDI_MODULE, 0 otherwise.
|
|
|
|
pata_legacy.winbond= [HW,LIBATA]
|
|
Format: <int>
|
|
Set to non-zero to probe Winbond controllers. Use
|
|
the standard I/O port (0x130) if 1, otherwise the
|
|
value given is the I/O port to use (typically 0x1b0).
|
|
By default set to 1 if CONFIG_PATA_WINBOND_VLB_MODULE,
|
|
0 otherwise.
|
|
|
|
pata_platform.pio_mask= [HW,LIBATA]
|
|
Format: <int>
|
|
Supported PIO mode mask. Set individual bits to allow
|
|
the use of the respective PIO modes. Bit 0 is for
|
|
mode 0, bit 1 is for mode 1, and so on. Mode 0 only
|
|
allowed by default.
|
|
|
|
pause_on_oops=
|
|
Halt all CPUs after the first oops has been printed for
|
|
the specified number of seconds. This is to be used if
|
|
your oopses keep scrolling off the screen.
|
|
|
|
pcbit= [HW,ISDN]
|
|
|
|
pcd. [PARIDE]
|
|
See header of drivers/block/paride/pcd.c.
|
|
See also Documentation/admin-guide/blockdev/paride.rst.
|
|
|
|
pci=option[,option...] [PCI] various PCI subsystem options.
|
|
|
|
Some options herein operate on a specific device
|
|
or a set of devices (<pci_dev>). These are
|
|
specified in one of the following formats:
|
|
|
|
[<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]*
|
|
pci:<vendor>:<device>[:<subvendor>:<subdevice>]
|
|
|
|
Note: the first format specifies a PCI
|
|
bus/device/function address which may change
|
|
if new hardware is inserted, if motherboard
|
|
firmware changes, or due to changes caused
|
|
by other kernel parameters. If the
|
|
domain is left unspecified, it is
|
|
taken to be zero. Optionally, a path
|
|
to a device through multiple device/function
|
|
addresses can be specified after the base
|
|
address (this is more robust against
|
|
renumbering issues). The second format
|
|
selects devices using IDs from the
|
|
configuration space which may match multiple
|
|
devices in the system.
|
|
|
|
earlydump dump PCI config space before the kernel
|
|
changes anything
|
|
off [X86] don't probe for the PCI bus
|
|
bios [X86-32] force use of PCI BIOS, don't access
|
|
the hardware directly. Use this if your machine
|
|
has a non-standard PCI host bridge.
|
|
nobios [X86-32] disallow use of PCI BIOS, only direct
|
|
hardware access methods are allowed. Use this
|
|
if you experience crashes upon bootup and you
|
|
suspect they are caused by the BIOS.
|
|
conf1 [X86] Force use of PCI Configuration Access
|
|
Mechanism 1 (config address in IO port 0xCF8,
|
|
data in IO port 0xCFC, both 32-bit).
|
|
conf2 [X86] Force use of PCI Configuration Access
|
|
Mechanism 2 (IO port 0xCF8 is an 8-bit port for
|
|
the function, IO port 0xCFA, also 8-bit, sets
|
|
bus number. The config space is then accessed
|
|
through ports 0xC000-0xCFFF).
|
|
See http://wiki.osdev.org/PCI for more info
|
|
on the configuration access mechanisms.
|
|
noaer [PCIE] If the PCIEAER kernel config parameter is
|
|
enabled, this kernel boot option can be used to
|
|
disable the use of PCIE advanced error reporting.
|
|
nodomains [PCI] Disable support for multiple PCI
|
|
root domains (aka PCI segments, in ACPI-speak).
|
|
nommconf [X86] Disable use of MMCONFIG for PCI
|
|
Configuration
|
|
check_enable_amd_mmconf [X86] check for and enable
|
|
properly configured MMIO access to PCI
|
|
config space on AMD family 10h CPU
|
|
nomsi [MSI] If the PCI_MSI kernel config parameter is
|
|
enabled, this kernel boot option can be used to
|
|
disable the use of MSI interrupts system-wide.
|
|
noioapicquirk [APIC] Disable all boot interrupt quirks.
|
|
Safety option to keep boot IRQs enabled. This
|
|
should never be necessary.
|
|
ioapicreroute [APIC] Enable rerouting of boot IRQs to the
|
|
primary IO-APIC for bridges that cannot disable
|
|
boot IRQs. This fixes a source of spurious IRQs
|
|
when the system masks IRQs.
|
|
noioapicreroute [APIC] Disable workaround that uses the
|
|
boot IRQ equivalent of an IRQ that connects to
|
|
a chipset where boot IRQs cannot be disabled.
|
|
The opposite of ioapicreroute.
|
|
biosirq [X86-32] Use PCI BIOS calls to get the interrupt
|
|
routing table. These calls are known to be buggy
|
|
on several machines and they hang the machine
|
|
when used, but on other computers it's the only
|
|
way to get the interrupt routing table. Try
|
|
this option if the kernel is unable to allocate
|
|
IRQs or discover secondary PCI buses on your
|
|
motherboard.
|
|
rom [X86] Assign address space to expansion ROMs.
|
|
Use with caution as certain devices share
|
|
address decoders between ROMs and other
|
|
resources.
|
|
norom [X86] Do not assign address space to
|
|
expansion ROMs that do not already have
|
|
BIOS assigned address ranges.
|
|
nobar [X86] Do not assign address space to the
|
|
BARs that weren't assigned by the BIOS.
|
|
irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
|
|
assigned automatically to PCI devices. You can
|
|
make the kernel exclude IRQs of your ISA cards
|
|
this way.
|
|
pirqaddr=0xAAAAA [X86] Specify the physical address
|
|
of the PIRQ table (normally generated
|
|
by the BIOS) if it is outside the
|
|
F0000h-100000h range.
|
|
lastbus=N [X86] Scan all buses thru bus #N. Can be
|
|
useful if the kernel is unable to find your
|
|
secondary buses and you want to tell it
|
|
explicitly which ones they are.
|
|
assign-busses [X86] Always assign all PCI bus
|
|
numbers ourselves, overriding
|
|
whatever the firmware may have done.
|
|
usepirqmask [X86] Honor the possible IRQ mask stored
|
|
in the BIOS $PIR table. This is needed on
|
|
some systems with broken BIOSes, notably
|
|
some HP Pavilion N5400 and Omnibook XE3
|
|
notebooks. This will have no effect if ACPI
|
|
IRQ routing is enabled.
|
|
noacpi [X86] Do not use ACPI for IRQ routing
|
|
or for PCI scanning.
|
|
use_crs [X86] Use PCI host bridge window information
|
|
from ACPI. On BIOSes from 2008 or later, this
|
|
is enabled by default. If you need to use this,
|
|
please report a bug.
|
|
nocrs [X86] Ignore PCI host bridge windows from ACPI.
|
|
If you need to use this, please report a bug.
|
|
routeirq Do IRQ routing for all PCI devices.
|
|
This is normally done in pci_enable_device(),
|
|
so this option is a temporary workaround
|
|
for broken drivers that don't call it.
|
|
skip_isa_align [X86] do not align io start addr, so can
|
|
handle more pci cards
|
|
noearly [X86] Don't do any early type 1 scanning.
|
|
This might help on some broken boards which
|
|
machine check when some devices' config space
|
|
is read. But various workarounds are disabled
|
|
and some IOMMU drivers will not work.
|
|
bfsort Sort PCI devices into breadth-first order.
|
|
This sorting is done to get a device
|
|
order compatible with older (<= 2.4) kernels.
|
|
nobfsort Don't sort PCI devices into breadth-first order.
|
|
pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
|
|
tuning and use the BIOS-configured MPS defaults.
|
|
pcie_bus_safe Set every device's MPS to the largest value
|
|
supported by all devices below the root complex.
|
|
pcie_bus_perf Set device MPS to the largest allowable MPS
|
|
based on its parent bus. Also set MRRS (Max
|
|
Read Request Size) to the largest supported
|
|
value (no larger than the MPS that the device
|
|
or bus can support) for best performance.
|
|
pcie_bus_peer2peer Set every device's MPS to 128B, which
|
|
every device is guaranteed to support. This
|
|
configuration allows peer-to-peer DMA between
|
|
any pair of devices, possibly at the cost of
|
|
reduced performance. This also guarantees
|
|
that hot-added devices will work.
|
|
cbiosize=nn[KMG] The fixed amount of bus space which is
|
|
reserved for the CardBus bridge's IO window.
|
|
The default value is 256 bytes.
|
|
cbmemsize=nn[KMG] The fixed amount of bus space which is
|
|
reserved for the CardBus bridge's memory
|
|
window. The default value is 64 megabytes.
|
|
resource_alignment=
|
|
Format:
|
|
[<order of align>@]<pci_dev>[; ...]
|
|
Specifies alignment and device to reassign
|
|
aligned memory resources. How to
|
|
specify the device is described above.
|
|
If <order of align> is not specified,
|
|
PAGE_SIZE is used as alignment.
|
|
A PCI-PCI bridge can be specified if resource
|
|
windows need to be expanded.
|
|
To specify the alignment for several
|
|
instances of a device, the PCI vendor,
|
|
device, subvendor, and subdevice may be
|
|
specified, e.g., 12@pci:8086:9c22:103c:198f
|
|
for 4096-byte alignment.
|
|
ecrc= Enable/disable PCIe ECRC (transaction layer
|
|
end-to-end CRC checking).
|
|
bios: Use BIOS/firmware settings. This is the
|
|
the default.
|
|
off: Turn ECRC off
|
|
on: Turn ECRC on.
|
|
hpiosize=nn[KMG] The fixed amount of bus space which is
|
|
reserved for hotplug bridge's IO window.
|
|
Default size is 256 bytes.
|
|
hpmmiosize=nn[KMG] The fixed amount of bus space which is
|
|
reserved for hotplug bridge's MMIO window.
|
|
Default size is 2 megabytes.
|
|
hpmmioprefsize=nn[KMG] The fixed amount of bus space which is
|
|
reserved for hotplug bridge's MMIO_PREF window.
|
|
Default size is 2 megabytes.
|
|
hpmemsize=nn[KMG] The fixed amount of bus space which is
|
|
reserved for hotplug bridge's MMIO and
|
|
MMIO_PREF window.
|
|
Default size is 2 megabytes.
|
|
hpbussize=nn The minimum amount of additional bus numbers
|
|
reserved for buses below a hotplug bridge.
|
|
Default is 1.
|
|
realloc= Enable/disable reallocating PCI bridge resources
|
|
if allocations done by BIOS are too small to
|
|
accommodate resources required by all child
|
|
devices.
|
|
off: Turn realloc off
|
|
on: Turn realloc on
|
|
realloc same as realloc=on
|
|
noari do not use PCIe ARI.
|
|
noats [PCIE, Intel-IOMMU, AMD-IOMMU]
|
|
do not use PCIe ATS (and IOMMU device IOTLB).
|
|
pcie_scan_all Scan all possible PCIe devices. Otherwise we
|
|
only look for one device below a PCIe downstream
|
|
port.
|
|
big_root_window Try to add a big 64bit memory window to the PCIe
|
|
root complex on AMD CPUs. Some GFX hardware
|
|
can resize a BAR to allow access to all VRAM.
|
|
Adding the window is slightly risky (it may
|
|
conflict with unreported devices), so this
|
|
taints the kernel.
|
|
disable_acs_redir=<pci_dev>[; ...]
|
|
Specify one or more PCI devices (in the format
|
|
specified above) separated by semicolons.
|
|
Each device specified will have the PCI ACS
|
|
redirect capabilities forced off which will
|
|
allow P2P traffic between devices through
|
|
bridges without forcing it upstream. Note:
|
|
this removes isolation between devices and
|
|
may put more devices in an IOMMU group.
|
|
force_floating [S390] Force usage of floating interrupts.
|
|
nomio [S390] Do not use MIO instructions.
|
|
norid [S390] ignore the RID field and force use of
|
|
one PCI domain per PCI function
|
|
|
|
pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
|
|
Management.
|
|
off Disable ASPM.
|
|
force Enable ASPM even on devices that claim not to support it.
|
|
WARNING: Forcing ASPM on may cause system lockups.
|
|
|
|
pcie_ports= [PCIE] PCIe port services handling:
|
|
native Use native PCIe services (PME, AER, DPC, PCIe hotplug)
|
|
even if the platform doesn't give the OS permission to
|
|
use them. This may cause conflicts if the platform
|
|
also tries to use these services.
|
|
dpc-native Use native PCIe service for DPC only. May
|
|
cause conflicts if firmware uses AER or DPC.
|
|
compat Disable native PCIe services (PME, AER, DPC, PCIe
|
|
hotplug).
|
|
|
|
pcie_port_pm= [PCIE] PCIe port power management handling:
|
|
off Disable power management of all PCIe ports
|
|
force Forcibly enable power management of all PCIe ports
|
|
|
|
pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
|
|
nomsi Do not use MSI for native PCIe PME signaling (this makes
|
|
all PCIe root ports use INTx for all services).
|
|
|
|
pcmv= [HW,PCMCIA] BadgePAD 4
|
|
|
|
pd_ignore_unused
|
|
[PM]
|
|
Keep all power-domains already enabled by bootloader on,
|
|
even if no driver has claimed them. This is useful
|
|
for debug and development, but should not be
|
|
needed on a platform with proper driver support.
|
|
|
|
pd. [PARIDE]
|
|
See Documentation/admin-guide/blockdev/paride.rst.
|
|
|
|
pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
|
|
boot time.
|
|
Format: { 0 | 1 }
|
|
See arch/parisc/kernel/pdc_chassis.c
|
|
|
|
percpu_alloc= Select which percpu first chunk allocator to use.
|
|
Currently supported values are "embed" and "page".
|
|
Archs may support subset or none of the selections.
|
|
See comments in mm/percpu.c for details on each
|
|
allocator. This parameter is primarily for debugging
|
|
and performance comparison.
|
|
|
|
pf. [PARIDE]
|
|
See Documentation/admin-guide/blockdev/paride.rst.
|
|
|
|
pg. [PARIDE]
|
|
See Documentation/admin-guide/blockdev/paride.rst.
|
|
|
|
pirq= [SMP,APIC] Manual mp-table setup
|
|
See Documentation/x86/i386/IO-APIC.rst.
|
|
|
|
plip= [PPT,NET] Parallel port network link
|
|
Format: { parport<nr> | timid | 0 }
|
|
See also Documentation/admin-guide/parport.rst.
|
|
|
|
pmtmr= [X86] Manual setup of pmtmr I/O Port.
|
|
Override pmtimer IOPort with a hex value.
|
|
e.g. pmtmr=0x508
|
|
|
|
pm_debug_messages [SUSPEND,KNL]
|
|
Enable suspend/resume debug messages during boot up.
|
|
|
|
pnp.debug=1 [PNP]
|
|
Enable PNP debug messages (depends on the
|
|
CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
|
|
via /sys/module/pnp/parameters/debug. We always show
|
|
current resource usage; turning this on also shows
|
|
possible settings and some assignment information.
|
|
|
|
pnpacpi= [ACPI]
|
|
{ off }
|
|
|
|
pnpbios= [ISAPNP]
|
|
{ on | off | curr | res | no-curr | no-res }
|
|
|
|
pnp_reserve_irq=
|
|
[ISAPNP] Exclude IRQs for the autoconfiguration
|
|
|
|
pnp_reserve_dma=
|
|
[ISAPNP] Exclude DMAs for the autoconfiguration
|
|
|
|
pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
|
|
Ranges are in pairs (I/O port base and size).
|
|
|
|
pnp_reserve_mem=
|
|
[ISAPNP] Exclude memory regions for the
|
|
autoconfiguration.
|
|
Ranges are in pairs (memory base and size).
|
|
|
|
ports= [IP_VS_FTP] IPVS ftp helper module
|
|
Default is 21.
|
|
Up to 8 (IP_VS_APP_MAX_PORTS) ports
|
|
may be specified.
|
|
Format: <port>,<port>....
|
|
|
|
powersave=off [PPC] This option disables power saving features.
|
|
It specifically disables cpuidle and sets the
|
|
platform machine description specific power_save
|
|
function to NULL. On Idle the CPU just reduces
|
|
execution priority.
|
|
|
|
ppc_strict_facility_enable
|
|
[PPC] This option catches any kernel floating point,
|
|
Altivec, VSX and SPE outside of regions specifically
|
|
allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
|
|
There is some performance impact when enabling this.
|
|
|
|
ppc_tm= [PPC]
|
|
Format: {"off"}
|
|
Disable Hardware Transactional Memory
|
|
|
|
preempt= [KNL]
|
|
Select preemption mode if you have CONFIG_PREEMPT_DYNAMIC
|
|
none - Limited to cond_resched() calls
|
|
voluntary - Limited to cond_resched() and might_sleep() calls
|
|
full - Any section that isn't explicitly preempt disabled
|
|
can be preempted anytime.
|
|
|
|
print-fatal-signals=
|
|
[KNL] debug: print fatal signals
|
|
|
|
If enabled, warn about various signal handling
|
|
related application anomalies: too many signals,
|
|
too many POSIX.1 timers, fatal signals causing a
|
|
coredump - etc.
|
|
|
|
If you hit the warning due to signal overflow,
|
|
you might want to try "ulimit -i unlimited".
|
|
|
|
default: off.
|
|
|
|
printk.always_kmsg_dump=
|
|
Trigger kmsg_dump for cases other than kernel oops or
|
|
panics
|
|
Format: <bool> (1/Y/y=enable, 0/N/n=disable)
|
|
default: disabled
|
|
|
|
printk.devkmsg={on,off,ratelimit}
|
|
Control writing to /dev/kmsg.
|
|
on - unlimited logging to /dev/kmsg from userspace
|
|
off - logging to /dev/kmsg disabled
|
|
ratelimit - ratelimit the logging
|
|
Default: ratelimit
|
|
|
|
printk.time= Show timing data prefixed to each printk message line
|
|
Format: <bool> (1/Y/y=enable, 0/N/n=disable)
|
|
|
|
processor.max_cstate= [HW,ACPI]
|
|
Limit processor to maximum C-state
|
|
max_cstate=9 overrides any DMI blacklist limit.
|
|
|
|
processor.nocst [HW,ACPI]
|
|
Ignore the _CST method to determine C-states,
|
|
instead using the legacy FADT method
|
|
|
|
profile= [KNL] Enable kernel profiling via /proc/profile
|
|
Format: [<profiletype>,]<number>
|
|
Param: <profiletype>: "schedule", "sleep", or "kvm"
|
|
[defaults to kernel profiling]
|
|
Param: "schedule" - profile schedule points.
|
|
Param: "sleep" - profile D-state sleeping (millisecs).
|
|
Requires CONFIG_SCHEDSTATS
|
|
Param: "kvm" - profile VM exits.
|
|
Param: <number> - step/bucket size as a power of 2 for
|
|
statistical time based profiling.
|
|
|
|
prompt_ramdisk= [RAM] [Deprecated]
|
|
|
|
prot_virt= [S390] enable hosting protected virtual machines
|
|
isolated from the hypervisor (if hardware supports
|
|
that).
|
|
Format: <bool>
|
|
|
|
psi= [KNL] Enable or disable pressure stall information
|
|
tracking.
|
|
Format: <bool>
|
|
|
|
psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
|
|
probe for; one of (bare|imps|exps|lifebook|any).
|
|
psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
|
|
per second.
|
|
psmouse.resetafter= [HW,MOUSE]
|
|
Try to reset the device after so many bad packets
|
|
(0 = never).
|
|
psmouse.resolution=
|
|
[HW,MOUSE] Set desired mouse resolution, in dpi.
|
|
psmouse.smartscroll=
|
|
[HW,MOUSE] Controls Logitech smartscroll autorepeat.
|
|
0 = disabled, 1 = enabled (default).
|
|
|
|
pstore.backend= Specify the name of the pstore backend to use
|
|
|
|
pt. [PARIDE]
|
|
See Documentation/admin-guide/blockdev/paride.rst.
|
|
|
|
pti= [X86-64] Control Page Table Isolation of user and
|
|
kernel address spaces. Disabling this feature
|
|
removes hardening, but improves performance of
|
|
system calls and interrupts.
|
|
|
|
on - unconditionally enable
|
|
off - unconditionally disable
|
|
auto - kernel detects whether your CPU model is
|
|
vulnerable to issues that PTI mitigates
|
|
|
|
Not specifying this option is equivalent to pti=auto.
|
|
|
|
nopti [X86-64]
|
|
Equivalent to pti=off
|
|
|
|
pty.legacy_count=
|
|
[KNL] Number of legacy pty's. Overwrites compiled-in
|
|
default number.
|
|
|
|
quiet [KNL] Disable most log messages
|
|
|
|
r128= [HW,DRM]
|
|
|
|
raid= [HW,RAID]
|
|
See Documentation/admin-guide/md.rst.
|
|
|
|
ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
|
|
See Documentation/admin-guide/blockdev/ramdisk.rst.
|
|
|
|
ramdisk_start= [RAM] RAM disk image start address
|
|
|
|
random.trust_cpu={on,off}
|
|
[KNL] Enable or disable trusting the use of the
|
|
CPU's random number generator (if available) to
|
|
fully seed the kernel's CRNG. Default is controlled
|
|
by CONFIG_RANDOM_TRUST_CPU.
|
|
|
|
randomize_kstack_offset=
|
|
[KNL] Enable or disable kernel stack offset
|
|
randomization, which provides roughly 5 bits of
|
|
entropy, frustrating memory corruption attacks
|
|
that depend on stack address determinism or
|
|
cross-syscall address exposures. This is only
|
|
available on architectures that have defined
|
|
CONFIG_HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET.
|
|
Format: <bool> (1/Y/y=enable, 0/N/n=disable)
|
|
Default is CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT.
|
|
|
|
ras=option[,option,...] [KNL] RAS-specific options
|
|
|
|
cec_disable [X86]
|
|
Disable the Correctable Errors Collector,
|
|
see CONFIG_RAS_CEC help text.
|
|
|
|
rcu_nocbs= [KNL]
|
|
The argument is a cpu list, as described above.
|
|
|
|
In kernels built with CONFIG_RCU_NOCB_CPU=y, set
|
|
the specified list of CPUs to be no-callback CPUs.
|
|
Invocation of these CPUs' RCU callbacks will be
|
|
offloaded to "rcuox/N" kthreads created for that
|
|
purpose, where "x" is "p" for RCU-preempt, and
|
|
"s" for RCU-sched, and "N" is the CPU number.
|
|
This reduces OS jitter on the offloaded CPUs,
|
|
which can be useful for HPC and real-time
|
|
workloads. It can also improve energy efficiency
|
|
for asymmetric multiprocessors.
|
|
|
|
rcu_nocb_poll [KNL]
|
|
Rather than requiring that offloaded CPUs
|
|
(specified by rcu_nocbs= above) explicitly
|
|
awaken the corresponding "rcuoN" kthreads,
|
|
make these kthreads poll for callbacks.
|
|
This improves the real-time response for the
|
|
offloaded CPUs by relieving them of the need to
|
|
wake up the corresponding kthread, but degrades
|
|
energy efficiency by requiring that the kthreads
|
|
periodically wake up to do the polling.
|
|
|
|
rcutree.blimit= [KNL]
|
|
Set maximum number of finished RCU callbacks to
|
|
process in one batch.
|
|
|
|
rcutree.dump_tree= [KNL]
|
|
Dump the structure of the rcu_node combining tree
|
|
out at early boot. This is used for diagnostic
|
|
purposes, to verify correct tree setup.
|
|
|
|
rcutree.gp_cleanup_delay= [KNL]
|
|
Set the number of jiffies to delay each step of
|
|
RCU grace-period cleanup.
|
|
|
|
rcutree.gp_init_delay= [KNL]
|
|
Set the number of jiffies to delay each step of
|
|
RCU grace-period initialization.
|
|
|
|
rcutree.gp_preinit_delay= [KNL]
|
|
Set the number of jiffies to delay each step of
|
|
RCU grace-period pre-initialization, that is,
|
|
the propagation of recent CPU-hotplug changes up
|
|
the rcu_node combining tree.
|
|
|
|
rcutree.use_softirq= [KNL]
|
|
If set to zero, move all RCU_SOFTIRQ processing to
|
|
per-CPU rcuc kthreads. Defaults to a non-zero
|
|
value, meaning that RCU_SOFTIRQ is used by default.
|
|
Specify rcutree.use_softirq=0 to use rcuc kthreads.
|
|
|
|
But note that CONFIG_PREEMPT_RT=y kernels disable
|
|
this kernel boot parameter, forcibly setting it
|
|
to zero.
|
|
|
|
rcutree.rcu_fanout_exact= [KNL]
|
|
Disable autobalancing of the rcu_node combining
|
|
tree. This is used by rcutorture, and might
|
|
possibly be useful for architectures having high
|
|
cache-to-cache transfer latencies.
|
|
|
|
rcutree.rcu_fanout_leaf= [KNL]
|
|
Change the number of CPUs assigned to each
|
|
leaf rcu_node structure. Useful for very
|
|
large systems, which will choose the value 64,
|
|
and for NUMA systems with large remote-access
|
|
latencies, which will choose a value aligned
|
|
with the appropriate hardware boundaries.
|
|
|
|
rcutree.rcu_min_cached_objs= [KNL]
|
|
Minimum number of objects which are cached and
|
|
maintained per one CPU. Object size is equal
|
|
to PAGE_SIZE. The cache allows to reduce the
|
|
pressure to page allocator, also it makes the
|
|
whole algorithm to behave better in low memory
|
|
condition.
|
|
|
|
rcutree.jiffies_till_first_fqs= [KNL]
|
|
Set delay from grace-period initialization to
|
|
first attempt to force quiescent states.
|
|
Units are jiffies, minimum value is zero,
|
|
and maximum value is HZ.
|
|
|
|
rcutree.jiffies_till_next_fqs= [KNL]
|
|
Set delay between subsequent attempts to force
|
|
quiescent states. Units are jiffies, minimum
|
|
value is one, and maximum value is HZ.
|
|
|
|
rcutree.jiffies_till_sched_qs= [KNL]
|
|
Set required age in jiffies for a
|
|
given grace period before RCU starts
|
|
soliciting quiescent-state help from
|
|
rcu_note_context_switch() and cond_resched().
|
|
If not specified, the kernel will calculate
|
|
a value based on the most recent settings
|
|
of rcutree.jiffies_till_first_fqs
|
|
and rcutree.jiffies_till_next_fqs.
|
|
This calculated value may be viewed in
|
|
rcutree.jiffies_to_sched_qs. Any attempt to set
|
|
rcutree.jiffies_to_sched_qs will be cheerfully
|
|
overwritten.
|
|
|
|
rcutree.kthread_prio= [KNL,BOOT]
|
|
Set the SCHED_FIFO priority of the RCU per-CPU
|
|
kthreads (rcuc/N). This value is also used for
|
|
the priority of the RCU boost threads (rcub/N)
|
|
and for the RCU grace-period kthreads (rcu_bh,
|
|
rcu_preempt, and rcu_sched). If RCU_BOOST is
|
|
set, valid values are 1-99 and the default is 1
|
|
(the least-favored priority). Otherwise, when
|
|
RCU_BOOST is not set, valid values are 0-99 and
|
|
the default is zero (non-realtime operation).
|
|
|
|
rcutree.rcu_nocb_gp_stride= [KNL]
|
|
Set the number of NOCB callback kthreads in
|
|
each group, which defaults to the square root
|
|
of the number of CPUs. Larger numbers reduce
|
|
the wakeup overhead on the global grace-period
|
|
kthread, but increases that same overhead on
|
|
each group's NOCB grace-period kthread.
|
|
|
|
rcutree.qhimark= [KNL]
|
|
Set threshold of queued RCU callbacks beyond which
|
|
batch limiting is disabled.
|
|
|
|
rcutree.qlowmark= [KNL]
|
|
Set threshold of queued RCU callbacks below which
|
|
batch limiting is re-enabled.
|
|
|
|
rcutree.qovld= [KNL]
|
|
Set threshold of queued RCU callbacks beyond which
|
|
RCU's force-quiescent-state scan will aggressively
|
|
enlist help from cond_resched() and sched IPIs to
|
|
help CPUs more quickly reach quiescent states.
|
|
Set to less than zero to make this be set based
|
|
on rcutree.qhimark at boot time and to zero to
|
|
disable more aggressive help enlistment.
|
|
|
|
rcutree.rcu_idle_gp_delay= [KNL]
|
|
Set wakeup interval for idle CPUs that have
|
|
RCU callbacks (RCU_FAST_NO_HZ=y).
|
|
|
|
rcutree.rcu_kick_kthreads= [KNL]
|
|
Cause the grace-period kthread to get an extra
|
|
wake_up() if it sleeps three times longer than
|
|
it should at force-quiescent-state time.
|
|
This wake_up() will be accompanied by a
|
|
WARN_ONCE() splat and an ftrace_dump().
|
|
|
|
rcutree.rcu_unlock_delay= [KNL]
|
|
In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels,
|
|
this specifies an rcu_read_unlock()-time delay
|
|
in microseconds. This defaults to zero.
|
|
Larger delays increase the probability of
|
|
catching RCU pointer leaks, that is, buggy use
|
|
of RCU-protected pointers after the relevant
|
|
rcu_read_unlock() has completed.
|
|
|
|
rcutree.sysrq_rcu= [KNL]
|
|
Commandeer a sysrq key to dump out Tree RCU's
|
|
rcu_node tree with an eye towards determining
|
|
why a new grace period has not yet started.
|
|
|
|
rcuscale.gp_async= [KNL]
|
|
Measure performance of asynchronous
|
|
grace-period primitives such as call_rcu().
|
|
|
|
rcuscale.gp_async_max= [KNL]
|
|
Specify the maximum number of outstanding
|
|
callbacks per writer thread. When a writer
|
|
thread exceeds this limit, it invokes the
|
|
corresponding flavor of rcu_barrier() to allow
|
|
previously posted callbacks to drain.
|
|
|
|
rcuscale.gp_exp= [KNL]
|
|
Measure performance of expedited synchronous
|
|
grace-period primitives.
|
|
|
|
rcuscale.holdoff= [KNL]
|
|
Set test-start holdoff period. The purpose of
|
|
this parameter is to delay the start of the
|
|
test until boot completes in order to avoid
|
|
interference.
|
|
|
|
rcuscale.kfree_rcu_test= [KNL]
|
|
Set to measure performance of kfree_rcu() flooding.
|
|
|
|
rcuscale.kfree_rcu_test_double= [KNL]
|
|
Test the double-argument variant of kfree_rcu().
|
|
If this parameter has the same value as
|
|
rcuscale.kfree_rcu_test_single, both the single-
|
|
and double-argument variants are tested.
|
|
|
|
rcuscale.kfree_rcu_test_single= [KNL]
|
|
Test the single-argument variant of kfree_rcu().
|
|
If this parameter has the same value as
|
|
rcuscale.kfree_rcu_test_double, both the single-
|
|
and double-argument variants are tested.
|
|
|
|
rcuscale.kfree_nthreads= [KNL]
|
|
The number of threads running loops of kfree_rcu().
|
|
|
|
rcuscale.kfree_alloc_num= [KNL]
|
|
Number of allocations and frees done in an iteration.
|
|
|
|
rcuscale.kfree_loops= [KNL]
|
|
Number of loops doing rcuscale.kfree_alloc_num number
|
|
of allocations and frees.
|
|
|
|
rcuscale.nreaders= [KNL]
|
|
Set number of RCU readers. The value -1 selects
|
|
N, where N is the number of CPUs. A value
|
|
"n" less than -1 selects N-n+1, where N is again
|
|
the number of CPUs. For example, -2 selects N
|
|
(the number of CPUs), -3 selects N+1, and so on.
|
|
A value of "n" less than or equal to -N selects
|
|
a single reader.
|
|
|
|
rcuscale.nwriters= [KNL]
|
|
Set number of RCU writers. The values operate
|
|
the same as for rcuscale.nreaders.
|
|
N, where N is the number of CPUs
|
|
|
|
rcuscale.perf_type= [KNL]
|
|
Specify the RCU implementation to test.
|
|
|
|
rcuscale.shutdown= [KNL]
|
|
Shut the system down after performance tests
|
|
complete. This is useful for hands-off automated
|
|
testing.
|
|
|
|
rcuscale.verbose= [KNL]
|
|
Enable additional printk() statements.
|
|
|
|
rcuscale.writer_holdoff= [KNL]
|
|
Write-side holdoff between grace periods,
|
|
in microseconds. The default of zero says
|
|
no holdoff.
|
|
|
|
rcutorture.fqs_duration= [KNL]
|
|
Set duration of force_quiescent_state bursts
|
|
in microseconds.
|
|
|
|
rcutorture.fqs_holdoff= [KNL]
|
|
Set holdoff time within force_quiescent_state bursts
|
|
in microseconds.
|
|
|
|
rcutorture.fqs_stutter= [KNL]
|
|
Set wait time between force_quiescent_state bursts
|
|
in seconds.
|
|
|
|
rcutorture.fwd_progress= [KNL]
|
|
Enable RCU grace-period forward-progress testing
|
|
for the types of RCU supporting this notion.
|
|
|
|
rcutorture.fwd_progress_div= [KNL]
|
|
Specify the fraction of a CPU-stall-warning
|
|
period to do tight-loop forward-progress testing.
|
|
|
|
rcutorture.fwd_progress_holdoff= [KNL]
|
|
Number of seconds to wait between successive
|
|
forward-progress tests.
|
|
|
|
rcutorture.fwd_progress_need_resched= [KNL]
|
|
Enclose cond_resched() calls within checks for
|
|
need_resched() during tight-loop forward-progress
|
|
testing.
|
|
|
|
rcutorture.gp_cond= [KNL]
|
|
Use conditional/asynchronous update-side
|
|
primitives, if available.
|
|
|
|
rcutorture.gp_exp= [KNL]
|
|
Use expedited update-side primitives, if available.
|
|
|
|
rcutorture.gp_normal= [KNL]
|
|
Use normal (non-expedited) asynchronous
|
|
update-side primitives, if available.
|
|
|
|
rcutorture.gp_sync= [KNL]
|
|
Use normal (non-expedited) synchronous
|
|
update-side primitives, if available. If all
|
|
of rcutorture.gp_cond=, rcutorture.gp_exp=,
|
|
rcutorture.gp_normal=, and rcutorture.gp_sync=
|
|
are zero, rcutorture acts as if is interpreted
|
|
they are all non-zero.
|
|
|
|
rcutorture.irqreader= [KNL]
|
|
Run RCU readers from irq handlers, or, more
|
|
accurately, from a timer handler. Not all RCU
|
|
flavors take kindly to this sort of thing.
|
|
|
|
rcutorture.leakpointer= [KNL]
|
|
Leak an RCU-protected pointer out of the reader.
|
|
This can of course result in splats, and is
|
|
intended to test the ability of things like
|
|
CONFIG_RCU_STRICT_GRACE_PERIOD=y to detect
|
|
such leaks.
|
|
|
|
rcutorture.n_barrier_cbs= [KNL]
|
|
Set callbacks/threads for rcu_barrier() testing.
|
|
|
|
rcutorture.nfakewriters= [KNL]
|
|
Set number of concurrent RCU writers. These just
|
|
stress RCU, they don't participate in the actual
|
|
test, hence the "fake".
|
|
|
|
rcutorture.nocbs_nthreads= [KNL]
|
|
Set number of RCU callback-offload togglers.
|
|
Zero (the default) disables toggling.
|
|
|
|
rcutorture.nocbs_toggle= [KNL]
|
|
Set the delay in milliseconds between successive
|
|
callback-offload toggling attempts.
|
|
|
|
rcutorture.nreaders= [KNL]
|
|
Set number of RCU readers. The value -1 selects
|
|
N-1, where N is the number of CPUs. A value
|
|
"n" less than -1 selects N-n-2, where N is again
|
|
the number of CPUs. For example, -2 selects N
|
|
(the number of CPUs), -3 selects N+1, and so on.
|
|
|
|
rcutorture.object_debug= [KNL]
|
|
Enable debug-object double-call_rcu() testing.
|
|
|
|
rcutorture.onoff_holdoff= [KNL]
|
|
Set time (s) after boot for CPU-hotplug testing.
|
|
|
|
rcutorture.onoff_interval= [KNL]
|
|
Set time (jiffies) between CPU-hotplug operations,
|
|
or zero to disable CPU-hotplug testing.
|
|
|
|
rcutorture.read_exit= [KNL]
|
|
Set the number of read-then-exit kthreads used
|
|
to test the interaction of RCU updaters and
|
|
task-exit processing.
|
|
|
|
rcutorture.read_exit_burst= [KNL]
|
|
The number of times in a given read-then-exit
|
|
episode that a set of read-then-exit kthreads
|
|
is spawned.
|
|
|
|
rcutorture.read_exit_delay= [KNL]
|
|
The delay, in seconds, between successive
|
|
read-then-exit testing episodes.
|
|
|
|
rcutorture.shuffle_interval= [KNL]
|
|
Set task-shuffle interval (s). Shuffling tasks
|
|
allows some CPUs to go into dyntick-idle mode
|
|
during the rcutorture test.
|
|
|
|
rcutorture.shutdown_secs= [KNL]
|
|
Set time (s) after boot system shutdown. This
|
|
is useful for hands-off automated testing.
|
|
|
|
rcutorture.stall_cpu= [KNL]
|
|
Duration of CPU stall (s) to test RCU CPU stall
|
|
warnings, zero to disable.
|
|
|
|
rcutorture.stall_cpu_block= [KNL]
|
|
Sleep while stalling if set. This will result
|
|
in warnings from preemptible RCU in addition
|
|
to any other stall-related activity.
|
|
|
|
rcutorture.stall_cpu_holdoff= [KNL]
|
|
Time to wait (s) after boot before inducing stall.
|
|
|
|
rcutorture.stall_cpu_irqsoff= [KNL]
|
|
Disable interrupts while stalling if set.
|
|
|
|
rcutorture.stall_gp_kthread= [KNL]
|
|
Duration (s) of forced sleep within RCU
|
|
grace-period kthread to test RCU CPU stall
|
|
warnings, zero to disable. If both stall_cpu
|
|
and stall_gp_kthread are specified, the
|
|
kthread is starved first, then the CPU.
|
|
|
|
rcutorture.stat_interval= [KNL]
|
|
Time (s) between statistics printk()s.
|
|
|
|
rcutorture.stutter= [KNL]
|
|
Time (s) to stutter testing, for example, specifying
|
|
five seconds causes the test to run for five seconds,
|
|
wait for five seconds, and so on. This tests RCU's
|
|
ability to transition abruptly to and from idle.
|
|
|
|
rcutorture.test_boost= [KNL]
|
|
Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
|
|
"Maybe" means test if the RCU implementation
|
|
under test support RCU priority boosting.
|
|
|
|
rcutorture.test_boost_duration= [KNL]
|
|
Duration (s) of each individual boost test.
|
|
|
|
rcutorture.test_boost_interval= [KNL]
|
|
Interval (s) between each boost test.
|
|
|
|
rcutorture.test_no_idle_hz= [KNL]
|
|
Test RCU's dyntick-idle handling. See also the
|
|
rcutorture.shuffle_interval parameter.
|
|
|
|
rcutorture.torture_type= [KNL]
|
|
Specify the RCU implementation to test.
|
|
|
|
rcutorture.verbose= [KNL]
|
|
Enable additional printk() statements.
|
|
|
|
rcupdate.rcu_cpu_stall_ftrace_dump= [KNL]
|
|
Dump ftrace buffer after reporting RCU CPU
|
|
stall warning.
|
|
|
|
rcupdate.rcu_cpu_stall_suppress= [KNL]
|
|
Suppress RCU CPU stall warning messages.
|
|
|
|
rcupdate.rcu_cpu_stall_suppress_at_boot= [KNL]
|
|
Suppress RCU CPU stall warning messages and
|
|
rcutorture writer stall warnings that occur
|
|
during early boot, that is, during the time
|
|
before the init task is spawned.
|
|
|
|
rcupdate.rcu_cpu_stall_timeout= [KNL]
|
|
Set timeout for RCU CPU stall warning messages.
|
|
|
|
rcupdate.rcu_expedited= [KNL]
|
|
Use expedited grace-period primitives, for
|
|
example, synchronize_rcu_expedited() instead
|
|
of synchronize_rcu(). This reduces latency,
|
|
but can increase CPU utilization, degrade
|
|
real-time latency, and degrade energy efficiency.
|
|
No effect on CONFIG_TINY_RCU kernels.
|
|
|
|
rcupdate.rcu_normal= [KNL]
|
|
Use only normal grace-period primitives,
|
|
for example, synchronize_rcu() instead of
|
|
synchronize_rcu_expedited(). This improves
|
|
real-time latency, CPU utilization, and
|
|
energy efficiency, but can expose users to
|
|
increased grace-period latency. This parameter
|
|
overrides rcupdate.rcu_expedited. No effect on
|
|
CONFIG_TINY_RCU kernels.
|
|
|
|
rcupdate.rcu_normal_after_boot= [KNL]
|
|
Once boot has completed (that is, after
|
|
rcu_end_inkernel_boot() has been invoked), use
|
|
only normal grace-period primitives. No effect
|
|
on CONFIG_TINY_RCU kernels.
|
|
|
|
But note that CONFIG_PREEMPT_RT=y kernels enables
|
|
this kernel boot parameter, forcibly setting
|
|
it to the value one, that is, converting any
|
|
post-boot attempt at an expedited RCU grace
|
|
period to instead use normal non-expedited
|
|
grace-period processing.
|
|
|
|
rcupdate.rcu_task_ipi_delay= [KNL]
|
|
Set time in jiffies during which RCU tasks will
|
|
avoid sending IPIs, starting with the beginning
|
|
of a given grace period. Setting a large
|
|
number avoids disturbing real-time workloads,
|
|
but lengthens grace periods.
|
|
|
|
rcupdate.rcu_task_stall_timeout= [KNL]
|
|
Set timeout in jiffies for RCU task stall warning
|
|
messages. Disable with a value less than or equal
|
|
to zero.
|
|
|
|
rcupdate.rcu_self_test= [KNL]
|
|
Run the RCU early boot self tests
|
|
|
|
rdinit= [KNL]
|
|
Format: <full_path>
|
|
Run specified binary instead of /init from the ramdisk,
|
|
used for early userspace startup. See initrd.
|
|
|
|
rdrand= [X86]
|
|
force - Override the decision by the kernel to hide the
|
|
advertisement of RDRAND support (this affects
|
|
certain AMD processors because of buggy BIOS
|
|
support, specifically around the suspend/resume
|
|
path).
|
|
|
|
rdt= [HW,X86,RDT]
|
|
Turn on/off individual RDT features. List is:
|
|
cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
|
|
mba.
|
|
E.g. to turn on cmt and turn off mba use:
|
|
rdt=cmt,!mba
|
|
|
|
reboot= [KNL]
|
|
Format (x86 or x86_64):
|
|
[w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
|
|
[[,]s[mp]#### \
|
|
[[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
|
|
[[,]f[orce]
|
|
Where reboot_mode is one of warm (soft) or cold (hard) or gpio
|
|
(prefix with 'panic_' to set mode for panic
|
|
reboot only),
|
|
reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
|
|
reboot_force is either force or not specified,
|
|
reboot_cpu is s[mp]#### with #### being the processor
|
|
to be used for rebooting.
|
|
|
|
refscale.holdoff= [KNL]
|
|
Set test-start holdoff period. The purpose of
|
|
this parameter is to delay the start of the
|
|
test until boot completes in order to avoid
|
|
interference.
|
|
|
|
refscale.loops= [KNL]
|
|
Set the number of loops over the synchronization
|
|
primitive under test. Increasing this number
|
|
reduces noise due to loop start/end overhead,
|
|
but the default has already reduced the per-pass
|
|
noise to a handful of picoseconds on ca. 2020
|
|
x86 laptops.
|
|
|
|
refscale.nreaders= [KNL]
|
|
Set number of readers. The default value of -1
|
|
selects N, where N is roughly 75% of the number
|
|
of CPUs. A value of zero is an interesting choice.
|
|
|
|
refscale.nruns= [KNL]
|
|
Set number of runs, each of which is dumped onto
|
|
the console log.
|
|
|
|
refscale.readdelay= [KNL]
|
|
Set the read-side critical-section duration,
|
|
measured in microseconds.
|
|
|
|
refscale.scale_type= [KNL]
|
|
Specify the read-protection implementation to test.
|
|
|
|
refscale.shutdown= [KNL]
|
|
Shut down the system at the end of the performance
|
|
test. This defaults to 1 (shut it down) when
|
|
refscale is built into the kernel and to 0 (leave
|
|
it running) when refscale is built as a module.
|
|
|
|
refscale.verbose= [KNL]
|
|
Enable additional printk() statements.
|
|
|
|
refscale.verbose_batched= [KNL]
|
|
Batch the additional printk() statements. If zero
|
|
(the default) or negative, print everything. Otherwise,
|
|
print every Nth verbose statement, where N is the value
|
|
specified.
|
|
|
|
relax_domain_level=
|
|
[KNL, SMP] Set scheduler's default relax_domain_level.
|
|
See Documentation/admin-guide/cgroup-v1/cpusets.rst.
|
|
|
|
reserve= [KNL,BUGS] Force kernel to ignore I/O ports or memory
|
|
Format: <base1>,<size1>[,<base2>,<size2>,...]
|
|
Reserve I/O ports or memory so the kernel won't use
|
|
them. If <base> is less than 0x10000, the region
|
|
is assumed to be I/O ports; otherwise it is memory.
|
|
|
|
reservetop= [X86-32]
|
|
Format: nn[KMG]
|
|
Reserves a hole at the top of the kernel virtual
|
|
address space.
|
|
|
|
reservelow= [X86]
|
|
Format: nn[K]
|
|
Set the amount of memory to reserve for BIOS at
|
|
the bottom of the address space.
|
|
|
|
reset_devices [KNL] Force drivers to reset the underlying device
|
|
during initialization.
|
|
|
|
resume= [SWSUSP]
|
|
Specify the partition device for software suspend
|
|
Format:
|
|
{/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
|
|
|
|
resume_offset= [SWSUSP]
|
|
Specify the offset from the beginning of the partition
|
|
given by "resume=" at which the swap header is located,
|
|
in <PAGE_SIZE> units (needed only for swap files).
|
|
See Documentation/power/swsusp-and-swap-files.rst
|
|
|
|
resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
|
|
read the resume files
|
|
|
|
resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
|
|
Useful for devices that are detected asynchronously
|
|
(e.g. USB and MMC devices).
|
|
|
|
hibernate= [HIBERNATION]
|
|
noresume Don't check if there's a hibernation image
|
|
present during boot.
|
|
nocompress Don't compress/decompress hibernation images.
|
|
no Disable hibernation and resume.
|
|
protect_image Turn on image protection during restoration
|
|
(that will set all pages holding image data
|
|
during restoration read-only).
|
|
|
|
retain_initrd [RAM] Keep initrd memory after extraction
|
|
|
|
rfkill.default_state=
|
|
0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
|
|
etc. communication is blocked by default.
|
|
1 Unblocked.
|
|
|
|
rfkill.master_switch_mode=
|
|
0 The "airplane mode" button does nothing.
|
|
1 The "airplane mode" button toggles between everything
|
|
blocked and the previous configuration.
|
|
2 The "airplane mode" button toggles between everything
|
|
blocked and everything unblocked.
|
|
|
|
rhash_entries= [KNL,NET]
|
|
Set number of hash buckets for route cache
|
|
|
|
ring3mwait=disable
|
|
[KNL] Disable ring 3 MONITOR/MWAIT feature on supported
|
|
CPUs.
|
|
|
|
ro [KNL] Mount root device read-only on boot
|
|
|
|
rodata= [KNL]
|
|
on Mark read-only kernel memory as read-only (default).
|
|
off Leave read-only kernel memory writable for debugging.
|
|
|
|
rockchip.usb_uart
|
|
Enable the uart passthrough on the designated usb port
|
|
on Rockchip SoCs. When active, the signals of the
|
|
debug-uart get routed to the D+ and D- pins of the usb
|
|
port and the regular usb controller gets disabled.
|
|
|
|
root= [KNL] Root filesystem
|
|
See name_to_dev_t comment in init/do_mounts.c.
|
|
|
|
rootdelay= [KNL] Delay (in seconds) to pause before attempting to
|
|
mount the root filesystem
|
|
|
|
rootflags= [KNL] Set root filesystem mount option string
|
|
|
|
rootfstype= [KNL] Set root filesystem type
|
|
|
|
rootwait [KNL] Wait (indefinitely) for root device to show up.
|
|
Useful for devices that are detected asynchronously
|
|
(e.g. USB and MMC devices).
|
|
|
|
rproc_mem=nn[KMG][@address]
|
|
[KNL,ARM,CMA] Remoteproc physical memory block.
|
|
Memory area to be used by remote processor image,
|
|
managed by CMA.
|
|
|
|
rw [KNL] Mount root device read-write on boot
|
|
|
|
S [KNL] Run init in single mode
|
|
|
|
s390_iommu= [HW,S390]
|
|
Set s390 IOTLB flushing mode
|
|
strict
|
|
With strict flushing every unmap operation will result in
|
|
an IOTLB flush. Default is lazy flushing before reuse,
|
|
which is faster.
|
|
|
|
sa1100ir [NET]
|
|
See drivers/net/irda/sa1100_ir.c.
|
|
|
|
sbni= [NET] Granch SBNI12 leased line adapter
|
|
|
|
sched_verbose [KNL] Enables verbose scheduler debug messages.
|
|
|
|
schedstats= [KNL,X86] Enable or disable scheduled statistics.
|
|
Allowed values are enable and disable. This feature
|
|
incurs a small amount of overhead in the scheduler
|
|
but is useful for debugging and performance tuning.
|
|
|
|
sched_thermal_decay_shift=
|
|
[KNL, SMP] Set a decay shift for scheduler thermal
|
|
pressure signal. Thermal pressure signal follows the
|
|
default decay period of other scheduler pelt
|
|
signals(usually 32 ms but configurable). Setting
|
|
sched_thermal_decay_shift will left shift the decay
|
|
period for the thermal pressure signal by the shift
|
|
value.
|
|
i.e. with the default pelt decay period of 32 ms
|
|
sched_thermal_decay_shift thermal pressure decay pr
|
|
1 64 ms
|
|
2 128 ms
|
|
and so on.
|
|
Format: integer between 0 and 10
|
|
Default is 0.
|
|
|
|
scftorture.holdoff= [KNL]
|
|
Number of seconds to hold off before starting
|
|
test. Defaults to zero for module insertion and
|
|
to 10 seconds for built-in smp_call_function()
|
|
tests.
|
|
|
|
scftorture.longwait= [KNL]
|
|
Request ridiculously long waits randomly selected
|
|
up to the chosen limit in seconds. Zero (the
|
|
default) disables this feature. Please note
|
|
that requesting even small non-zero numbers of
|
|
seconds can result in RCU CPU stall warnings,
|
|
softlockup complaints, and so on.
|
|
|
|
scftorture.nthreads= [KNL]
|
|
Number of kthreads to spawn to invoke the
|
|
smp_call_function() family of functions.
|
|
The default of -1 specifies a number of kthreads
|
|
equal to the number of CPUs.
|
|
|
|
scftorture.onoff_holdoff= [KNL]
|
|
Number seconds to wait after the start of the
|
|
test before initiating CPU-hotplug operations.
|
|
|
|
scftorture.onoff_interval= [KNL]
|
|
Number seconds to wait between successive
|
|
CPU-hotplug operations. Specifying zero (which
|
|
is the default) disables CPU-hotplug operations.
|
|
|
|
scftorture.shutdown_secs= [KNL]
|
|
The number of seconds following the start of the
|
|
test after which to shut down the system. The
|
|
default of zero avoids shutting down the system.
|
|
Non-zero values are useful for automated tests.
|
|
|
|
scftorture.stat_interval= [KNL]
|
|
The number of seconds between outputting the
|
|
current test statistics to the console. A value
|
|
of zero disables statistics output.
|
|
|
|
scftorture.stutter_cpus= [KNL]
|
|
The number of jiffies to wait between each change
|
|
to the set of CPUs under test.
|
|
|
|
scftorture.use_cpus_read_lock= [KNL]
|
|
Use use_cpus_read_lock() instead of the default
|
|
preempt_disable() to disable CPU hotplug
|
|
while invoking one of the smp_call_function*()
|
|
functions.
|
|
|
|
scftorture.verbose= [KNL]
|
|
Enable additional printk() statements.
|
|
|
|
scftorture.weight_single= [KNL]
|
|
The probability weighting to use for the
|
|
smp_call_function_single() function with a zero
|
|
"wait" parameter. A value of -1 selects the
|
|
default if all other weights are -1. However,
|
|
if at least one weight has some other value, a
|
|
value of -1 will instead select a weight of zero.
|
|
|
|
scftorture.weight_single_wait= [KNL]
|
|
The probability weighting to use for the
|
|
smp_call_function_single() function with a
|
|
non-zero "wait" parameter. See weight_single.
|
|
|
|
scftorture.weight_many= [KNL]
|
|
The probability weighting to use for the
|
|
smp_call_function_many() function with a zero
|
|
"wait" parameter. See weight_single.
|
|
Note well that setting a high probability for
|
|
this weighting can place serious IPI load
|
|
on the system.
|
|
|
|
scftorture.weight_many_wait= [KNL]
|
|
The probability weighting to use for the
|
|
smp_call_function_many() function with a
|
|
non-zero "wait" parameter. See weight_single
|
|
and weight_many.
|
|
|
|
scftorture.weight_all= [KNL]
|
|
The probability weighting to use for the
|
|
smp_call_function_all() function with a zero
|
|
"wait" parameter. See weight_single and
|
|
weight_many.
|
|
|
|
scftorture.weight_all_wait= [KNL]
|
|
The probability weighting to use for the
|
|
smp_call_function_all() function with a
|
|
non-zero "wait" parameter. See weight_single
|
|
and weight_many.
|
|
|
|
skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
|
|
xtime_lock contention on larger systems, and/or RCU lock
|
|
contention on all systems with CONFIG_MAXSMP set.
|
|
Format: { "0" | "1" }
|
|
0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
|
|
1 -- enable.
|
|
Note: increases power consumption, thus should only be
|
|
enabled if running jitter sensitive (HPC/RT) workloads.
|
|
|
|
security= [SECURITY] Choose a legacy "major" security module to
|
|
enable at boot. This has been deprecated by the
|
|
"lsm=" parameter.
|
|
|
|
selinux= [SELINUX] Disable or enable SELinux at boot time.
|
|
Format: { "0" | "1" }
|
|
See security/selinux/Kconfig help text.
|
|
0 -- disable.
|
|
1 -- enable.
|
|
Default value is 1.
|
|
|
|
apparmor= [APPARMOR] Disable or enable AppArmor at boot time
|
|
Format: { "0" | "1" }
|
|
See security/apparmor/Kconfig help text
|
|
0 -- disable.
|
|
1 -- enable.
|
|
Default value is set via kernel config option.
|
|
|
|
serialnumber [BUGS=X86-32]
|
|
|
|
shapers= [NET]
|
|
Maximal number of shapers.
|
|
|
|
simeth= [IA-64]
|
|
simscsi=
|
|
|
|
slram= [HW,MTD]
|
|
|
|
slab_merge [MM]
|
|
Enable merging of slabs with similar size when the
|
|
kernel is built without CONFIG_SLAB_MERGE_DEFAULT.
|
|
|
|
slab_nomerge [MM]
|
|
Disable merging of slabs with similar size. May be
|
|
necessary if there is some reason to distinguish
|
|
allocs to different slabs, especially in hardened
|
|
environments where the risk of heap overflows and
|
|
layout control by attackers can usually be
|
|
frustrated by disabling merging. This will reduce
|
|
most of the exposure of a heap attack to a single
|
|
cache (risks via metadata attacks are mostly
|
|
unchanged). Debug options disable merging on their
|
|
own.
|
|
For more information see Documentation/vm/slub.rst.
|
|
|
|
slab_max_order= [MM, SLAB]
|
|
Determines the maximum allowed order for slabs.
|
|
A high setting may cause OOMs due to memory
|
|
fragmentation. Defaults to 1 for systems with
|
|
more than 32MB of RAM, 0 otherwise.
|
|
|
|
slub_debug[=options[,slabs][;[options[,slabs]]...] [MM, SLUB]
|
|
Enabling slub_debug allows one to determine the
|
|
culprit if slab objects become corrupted. Enabling
|
|
slub_debug can create guard zones around objects and
|
|
may poison objects when not in use. Also tracks the
|
|
last alloc / free. For more information see
|
|
Documentation/vm/slub.rst.
|
|
|
|
slub_max_order= [MM, SLUB]
|
|
Determines the maximum allowed order for slabs.
|
|
A high setting may cause OOMs due to memory
|
|
fragmentation. For more information see
|
|
Documentation/vm/slub.rst.
|
|
|
|
slub_min_objects= [MM, SLUB]
|
|
The minimum number of objects per slab. SLUB will
|
|
increase the slab order up to slub_max_order to
|
|
generate a sufficiently large slab able to contain
|
|
the number of objects indicated. The higher the number
|
|
of objects the smaller the overhead of tracking slabs
|
|
and the less frequently locks need to be acquired.
|
|
For more information see Documentation/vm/slub.rst.
|
|
|
|
slub_min_order= [MM, SLUB]
|
|
Determines the minimum page order for slabs. Must be
|
|
lower than slub_max_order.
|
|
For more information see Documentation/vm/slub.rst.
|
|
|
|
slub_merge [MM, SLUB]
|
|
Same with slab_merge.
|
|
|
|
slub_nomerge [MM, SLUB]
|
|
Same with slab_nomerge. This is supported for legacy.
|
|
See slab_nomerge for more information.
|
|
|
|
smart2= [HW]
|
|
Format: <io1>[,<io2>[,...,<io8>]]
|
|
|
|
smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
|
|
smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
|
|
smsc-ircc2.ircc_sir= [HW] SIR base I/O port
|
|
smsc-ircc2.ircc_fir= [HW] FIR base I/O port
|
|
smsc-ircc2.ircc_irq= [HW] IRQ line
|
|
smsc-ircc2.ircc_dma= [HW] DMA channel
|
|
smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
|
|
0: Toshiba Satellite 1800 (GP data pin select)
|
|
1: Fast pin select (default)
|
|
2: ATC IRMode
|
|
|
|
smt [KNL,S390] Set the maximum number of threads (logical
|
|
CPUs) to use per physical CPU on systems capable of
|
|
symmetric multithreading (SMT). Will be capped to the
|
|
actual hardware limit.
|
|
Format: <integer>
|
|
Default: -1 (no limit)
|
|
|
|
softlockup_panic=
|
|
[KNL] Should the soft-lockup detector generate panics.
|
|
Format: 0 | 1
|
|
|
|
A value of 1 instructs the soft-lockup detector
|
|
to panic the machine when a soft-lockup occurs. It is
|
|
also controlled by the kernel.softlockup_panic sysctl
|
|
and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the
|
|
respective build-time switch to that functionality.
|
|
|
|
softlockup_all_cpu_backtrace=
|
|
[KNL] Should the soft-lockup detector generate
|
|
backtraces on all cpus.
|
|
Format: 0 | 1
|
|
|
|
sonypi.*= [HW] Sony Programmable I/O Control Device driver
|
|
See Documentation/admin-guide/laptops/sonypi.rst
|
|
|
|
spectre_v2= [X86] Control mitigation of Spectre variant 2
|
|
(indirect branch speculation) vulnerability.
|
|
The default operation protects the kernel from
|
|
user space attacks.
|
|
|
|
on - unconditionally enable, implies
|
|
spectre_v2_user=on
|
|
off - unconditionally disable, implies
|
|
spectre_v2_user=off
|
|
auto - kernel detects whether your CPU model is
|
|
vulnerable
|
|
|
|
Selecting 'on' will, and 'auto' may, choose a
|
|
mitigation method at run time according to the
|
|
CPU, the available microcode, the setting of the
|
|
CONFIG_RETPOLINE configuration option, and the
|
|
compiler with which the kernel was built.
|
|
|
|
Selecting 'on' will also enable the mitigation
|
|
against user space to user space task attacks.
|
|
|
|
Selecting 'off' will disable both the kernel and
|
|
the user space protections.
|
|
|
|
Specific mitigations can also be selected manually:
|
|
|
|
retpoline - replace indirect branches
|
|
retpoline,generic - google's original retpoline
|
|
retpoline,amd - AMD-specific minimal thunk
|
|
|
|
Not specifying this option is equivalent to
|
|
spectre_v2=auto.
|
|
|
|
spectre_v2_user=
|
|
[X86] Control mitigation of Spectre variant 2
|
|
(indirect branch speculation) vulnerability between
|
|
user space tasks
|
|
|
|
on - Unconditionally enable mitigations. Is
|
|
enforced by spectre_v2=on
|
|
|
|
off - Unconditionally disable mitigations. Is
|
|
enforced by spectre_v2=off
|
|
|
|
prctl - Indirect branch speculation is enabled,
|
|
but mitigation can be enabled via prctl
|
|
per thread. The mitigation control state
|
|
is inherited on fork.
|
|
|
|
prctl,ibpb
|
|
- Like "prctl" above, but only STIBP is
|
|
controlled per thread. IBPB is issued
|
|
always when switching between different user
|
|
space processes.
|
|
|
|
seccomp
|
|
- Same as "prctl" above, but all seccomp
|
|
threads will enable the mitigation unless
|
|
they explicitly opt out.
|
|
|
|
seccomp,ibpb
|
|
- Like "seccomp" above, but only STIBP is
|
|
controlled per thread. IBPB is issued
|
|
always when switching between different
|
|
user space processes.
|
|
|
|
auto - Kernel selects the mitigation depending on
|
|
the available CPU features and vulnerability.
|
|
|
|
Default mitigation:
|
|
If CONFIG_SECCOMP=y then "seccomp", otherwise "prctl"
|
|
|
|
Not specifying this option is equivalent to
|
|
spectre_v2_user=auto.
|
|
|
|
spec_store_bypass_disable=
|
|
[HW] Control Speculative Store Bypass (SSB) Disable mitigation
|
|
(Speculative Store Bypass vulnerability)
|
|
|
|
Certain CPUs are vulnerable to an exploit against a
|
|
a common industry wide performance optimization known
|
|
as "Speculative Store Bypass" in which recent stores
|
|
to the same memory location may not be observed by
|
|
later loads during speculative execution. The idea
|
|
is that such stores are unlikely and that they can
|
|
be detected prior to instruction retirement at the
|
|
end of a particular speculation execution window.
|
|
|
|
In vulnerable processors, the speculatively forwarded
|
|
store can be used in a cache side channel attack, for
|
|
example to read memory to which the attacker does not
|
|
directly have access (e.g. inside sandboxed code).
|
|
|
|
This parameter controls whether the Speculative Store
|
|
Bypass optimization is used.
|
|
|
|
On x86 the options are:
|
|
|
|
on - Unconditionally disable Speculative Store Bypass
|
|
off - Unconditionally enable Speculative Store Bypass
|
|
auto - Kernel detects whether the CPU model contains an
|
|
implementation of Speculative Store Bypass and
|
|
picks the most appropriate mitigation. If the
|
|
CPU is not vulnerable, "off" is selected. If the
|
|
CPU is vulnerable the default mitigation is
|
|
architecture and Kconfig dependent. See below.
|
|
prctl - Control Speculative Store Bypass per thread
|
|
via prctl. Speculative Store Bypass is enabled
|
|
for a process by default. The state of the control
|
|
is inherited on fork.
|
|
seccomp - Same as "prctl" above, but all seccomp threads
|
|
will disable SSB unless they explicitly opt out.
|
|
|
|
Default mitigations:
|
|
X86: If CONFIG_SECCOMP=y "seccomp", otherwise "prctl"
|
|
|
|
On powerpc the options are:
|
|
|
|
on,auto - On Power8 and Power9 insert a store-forwarding
|
|
barrier on kernel entry and exit. On Power7
|
|
perform a software flush on kernel entry and
|
|
exit.
|
|
off - No action.
|
|
|
|
Not specifying this option is equivalent to
|
|
spec_store_bypass_disable=auto.
|
|
|
|
spia_io_base= [HW,MTD]
|
|
spia_fio_base=
|
|
spia_pedr=
|
|
spia_peddr=
|
|
|
|
split_lock_detect=
|
|
[X86] Enable split lock detection or bus lock detection
|
|
|
|
When enabled (and if hardware support is present), atomic
|
|
instructions that access data across cache line
|
|
boundaries will result in an alignment check exception
|
|
for split lock detection or a debug exception for
|
|
bus lock detection.
|
|
|
|
off - not enabled
|
|
|
|
warn - the kernel will emit rate-limited warnings
|
|
about applications triggering the #AC
|
|
exception or the #DB exception. This mode is
|
|
the default on CPUs that support split lock
|
|
detection or bus lock detection. Default
|
|
behavior is by #AC if both features are
|
|
enabled in hardware.
|
|
|
|
fatal - the kernel will send SIGBUS to applications
|
|
that trigger the #AC exception or the #DB
|
|
exception. Default behavior is by #AC if
|
|
both features are enabled in hardware.
|
|
|
|
If an #AC exception is hit in the kernel or in
|
|
firmware (i.e. not while executing in user mode)
|
|
the kernel will oops in either "warn" or "fatal"
|
|
mode.
|
|
|
|
#DB exception for bus lock is triggered only when
|
|
CPL > 0.
|
|
|
|
srbds= [X86,INTEL]
|
|
Control the Special Register Buffer Data Sampling
|
|
(SRBDS) mitigation.
|
|
|
|
Certain CPUs are vulnerable to an MDS-like
|
|
exploit which can leak bits from the random
|
|
number generator.
|
|
|
|
By default, this issue is mitigated by
|
|
microcode. However, the microcode fix can cause
|
|
the RDRAND and RDSEED instructions to become
|
|
much slower. Among other effects, this will
|
|
result in reduced throughput from /dev/urandom.
|
|
|
|
The microcode mitigation can be disabled with
|
|
the following option:
|
|
|
|
off: Disable mitigation and remove
|
|
performance impact to RDRAND and RDSEED
|
|
|
|
srcutree.counter_wrap_check [KNL]
|
|
Specifies how frequently to check for
|
|
grace-period sequence counter wrap for the
|
|
srcu_data structure's ->srcu_gp_seq_needed field.
|
|
The greater the number of bits set in this kernel
|
|
parameter, the less frequently counter wrap will
|
|
be checked for. Note that the bottom two bits
|
|
are ignored.
|
|
|
|
srcutree.exp_holdoff [KNL]
|
|
Specifies how many nanoseconds must elapse
|
|
since the end of the last SRCU grace period for
|
|
a given srcu_struct until the next normal SRCU
|
|
grace period will be considered for automatic
|
|
expediting. Set to zero to disable automatic
|
|
expediting.
|
|
|
|
ssbd= [ARM64,HW]
|
|
Speculative Store Bypass Disable control
|
|
|
|
On CPUs that are vulnerable to the Speculative
|
|
Store Bypass vulnerability and offer a
|
|
firmware based mitigation, this parameter
|
|
indicates how the mitigation should be used:
|
|
|
|
force-on: Unconditionally enable mitigation for
|
|
for both kernel and userspace
|
|
force-off: Unconditionally disable mitigation for
|
|
for both kernel and userspace
|
|
kernel: Always enable mitigation in the
|
|
kernel, and offer a prctl interface
|
|
to allow userspace to register its
|
|
interest in being mitigated too.
|
|
|
|
stack_guard_gap= [MM]
|
|
override the default stack gap protection. The value
|
|
is in page units and it defines how many pages prior
|
|
to (for stacks growing down) resp. after (for stacks
|
|
growing up) the main stack are reserved for no other
|
|
mapping. Default value is 256 pages.
|
|
|
|
stack_depot_disable= [KNL]
|
|
Setting this to true through kernel command line will
|
|
disable the stack depot thereby saving the static memory
|
|
consumed by the stack hash table. By default this is set
|
|
to false.
|
|
|
|
stacktrace [FTRACE]
|
|
Enabled the stack tracer on boot up.
|
|
|
|
stacktrace_filter=[function-list]
|
|
[FTRACE] Limit the functions that the stack tracer
|
|
will trace at boot up. function-list is a comma-separated
|
|
list of functions. This list can be changed at run
|
|
time by the stack_trace_filter file in the debugfs
|
|
tracing directory. Note, this enables stack tracing
|
|
and the stacktrace above is not needed.
|
|
|
|
sti= [PARISC,HW]
|
|
Format: <num>
|
|
Set the STI (builtin display/keyboard on the HP-PARISC
|
|
machines) console (graphic card) which should be used
|
|
as the initial boot-console.
|
|
See also comment in drivers/video/console/sticore.c.
|
|
|
|
sti_font= [HW]
|
|
See comment in drivers/video/console/sticore.c.
|
|
|
|
stifb= [HW]
|
|
Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
|
|
|
|
sunrpc.min_resvport=
|
|
sunrpc.max_resvport=
|
|
[NFS,SUNRPC]
|
|
SunRPC servers often require that client requests
|
|
originate from a privileged port (i.e. a port in the
|
|
range 0 < portnr < 1024).
|
|
An administrator who wishes to reserve some of these
|
|
ports for other uses may adjust the range that the
|
|
kernel's sunrpc client considers to be privileged
|
|
using these two parameters to set the minimum and
|
|
maximum port values.
|
|
|
|
sunrpc.svc_rpc_per_connection_limit=
|
|
[NFS,SUNRPC]
|
|
Limit the number of requests that the server will
|
|
process in parallel from a single connection.
|
|
The default value is 0 (no limit).
|
|
|
|
sunrpc.pool_mode=
|
|
[NFS]
|
|
Control how the NFS server code allocates CPUs to
|
|
service thread pools. Depending on how many NICs
|
|
you have and where their interrupts are bound, this
|
|
option will affect which CPUs will do NFS serving.
|
|
Note: this parameter cannot be changed while the
|
|
NFS server is running.
|
|
|
|
auto the server chooses an appropriate mode
|
|
automatically using heuristics
|
|
global a single global pool contains all CPUs
|
|
percpu one pool for each CPU
|
|
pernode one pool for each NUMA node (equivalent
|
|
to global on non-NUMA machines)
|
|
|
|
sunrpc.tcp_slot_table_entries=
|
|
sunrpc.udp_slot_table_entries=
|
|
[NFS,SUNRPC]
|
|
Sets the upper limit on the number of simultaneous
|
|
RPC calls that can be sent from the client to a
|
|
server. Increasing these values may allow you to
|
|
improve throughput, but will also increase the
|
|
amount of memory reserved for use by the client.
|
|
|
|
suspend.pm_test_delay=
|
|
[SUSPEND]
|
|
Sets the number of seconds to remain in a suspend test
|
|
mode before resuming the system (see
|
|
/sys/power/pm_test). Only available when CONFIG_PM_DEBUG
|
|
is set. Default value is 5.
|
|
|
|
svm= [PPC]
|
|
Format: { on | off | y | n | 1 | 0 }
|
|
This parameter controls use of the Protected
|
|
Execution Facility on pSeries.
|
|
|
|
swapaccount=[0|1]
|
|
[KNL] Enable accounting of swap in memory resource
|
|
controller if no parameter or 1 is given or disable
|
|
it if 0 is given (See Documentation/admin-guide/cgroup-v1/memory.rst)
|
|
|
|
swiotlb= [ARM,IA-64,PPC,MIPS,X86]
|
|
Format: { <int> | force | noforce }
|
|
<int> -- Number of I/O TLB slabs
|
|
force -- force using of bounce buffers even if they
|
|
wouldn't be automatically used by the kernel
|
|
noforce -- Never use bounce buffers (for debugging)
|
|
|
|
switches= [HW,M68k]
|
|
|
|
sysctl.*= [KNL]
|
|
Set a sysctl parameter, right before loading the init
|
|
process, as if the value was written to the respective
|
|
/proc/sys/... file. Both '.' and '/' are recognized as
|
|
separators. Unrecognized parameters and invalid values
|
|
are reported in the kernel log. Sysctls registered
|
|
later by a loaded module cannot be set this way.
|
|
Example: sysctl.vm.swappiness=40
|
|
|
|
sysfs.deprecated=0|1 [KNL]
|
|
Enable/disable old style sysfs layout for old udev
|
|
on older distributions. When this option is enabled
|
|
very new udev will not work anymore. When this option
|
|
is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
|
|
in older udev will not work anymore.
|
|
Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
|
|
the kernel configuration.
|
|
|
|
sysrq_always_enabled
|
|
[KNL]
|
|
Ignore sysrq setting - this boot parameter will
|
|
neutralize any effect of /proc/sys/kernel/sysrq.
|
|
Useful for debugging.
|
|
|
|
tcpmhash_entries= [KNL,NET]
|
|
Set the number of tcp_metrics_hash slots.
|
|
Default value is 8192 or 16384 depending on total
|
|
ram pages. This is used to specify the TCP metrics
|
|
cache size. See Documentation/networking/ip-sysctl.rst
|
|
"tcp_no_metrics_save" section for more details.
|
|
|
|
tdfx= [HW,DRM]
|
|
|
|
test_suspend= [SUSPEND][,N]
|
|
Specify "mem" (for Suspend-to-RAM) or "standby" (for
|
|
standby suspend) or "freeze" (for suspend type freeze)
|
|
as the system sleep state during system startup with
|
|
the optional capability to repeat N number of times.
|
|
The system is woken from this state using a
|
|
wakeup-capable RTC alarm.
|
|
|
|
thash_entries= [KNL,NET]
|
|
Set number of hash buckets for TCP connection
|
|
|
|
thermal.act= [HW,ACPI]
|
|
-1: disable all active trip points in all thermal zones
|
|
<degrees C>: override all lowest active trip points
|
|
|
|
thermal.crt= [HW,ACPI]
|
|
-1: disable all critical trip points in all thermal zones
|
|
<degrees C>: override all critical trip points
|
|
|
|
thermal.nocrt= [HW,ACPI]
|
|
Set to disable actions on ACPI thermal zone
|
|
critical and hot trip points.
|
|
|
|
thermal.off= [HW,ACPI]
|
|
1: disable ACPI thermal control
|
|
|
|
thermal.psv= [HW,ACPI]
|
|
-1: disable all passive trip points
|
|
<degrees C>: override all passive trip points to this
|
|
value
|
|
|
|
thermal.tzp= [HW,ACPI]
|
|
Specify global default ACPI thermal zone polling rate
|
|
<deci-seconds>: poll all this frequency
|
|
0: no polling (default)
|
|
|
|
threadirqs [KNL]
|
|
Force threading of all interrupt handlers except those
|
|
marked explicitly IRQF_NO_THREAD.
|
|
|
|
topology= [S390]
|
|
Format: {off | on}
|
|
Specify if the kernel should make use of the cpu
|
|
topology information if the hardware supports this.
|
|
The scheduler will make use of this information and
|
|
e.g. base its process migration decisions on it.
|
|
Default is on.
|
|
|
|
topology_updates= [KNL, PPC, NUMA]
|
|
Format: {off}
|
|
Specify if the kernel should ignore (off)
|
|
topology updates sent by the hypervisor to this
|
|
LPAR.
|
|
|
|
torture.disable_onoff_at_boot= [KNL]
|
|
Prevent the CPU-hotplug component of torturing
|
|
until after init has spawned.
|
|
|
|
torture.ftrace_dump_at_shutdown= [KNL]
|
|
Dump the ftrace buffer at torture-test shutdown,
|
|
even if there were no errors. This can be a
|
|
very costly operation when many torture tests
|
|
are running concurrently, especially on systems
|
|
with rotating-rust storage.
|
|
|
|
torture.verbose_sleep_frequency= [KNL]
|
|
Specifies how many verbose printk()s should be
|
|
emitted between each sleep. The default of zero
|
|
disables verbose-printk() sleeping.
|
|
|
|
torture.verbose_sleep_duration= [KNL]
|
|
Duration of each verbose-printk() sleep in jiffies.
|
|
|
|
tp720= [HW,PS2]
|
|
|
|
tpm_suspend_pcr=[HW,TPM]
|
|
Format: integer pcr id
|
|
Specify that at suspend time, the tpm driver
|
|
should extend the specified pcr with zeros,
|
|
as a workaround for some chips which fail to
|
|
flush the last written pcr on TPM_SaveState.
|
|
This will guarantee that all the other pcrs
|
|
are saved.
|
|
|
|
trace_buf_size=nn[KMG]
|
|
[FTRACE] will set tracing buffer size on each cpu.
|
|
|
|
trace_event=[event-list]
|
|
[FTRACE] Set and start specified trace events in order
|
|
to facilitate early boot debugging. The event-list is a
|
|
comma-separated list of trace events to enable. See
|
|
also Documentation/trace/events.rst
|
|
|
|
trace_options=[option-list]
|
|
[FTRACE] Enable or disable tracer options at boot.
|
|
The option-list is a comma delimited list of options
|
|
that can be enabled or disabled just as if you were
|
|
to echo the option name into
|
|
|
|
/sys/kernel/debug/tracing/trace_options
|
|
|
|
For example, to enable stacktrace option (to dump the
|
|
stack trace of each event), add to the command line:
|
|
|
|
trace_options=stacktrace
|
|
|
|
See also Documentation/trace/ftrace.rst "trace options"
|
|
section.
|
|
|
|
tp_printk[FTRACE]
|
|
Have the tracepoints sent to printk as well as the
|
|
tracing ring buffer. This is useful for early boot up
|
|
where the system hangs or reboots and does not give the
|
|
option for reading the tracing buffer or performing a
|
|
ftrace_dump_on_oops.
|
|
|
|
To turn off having tracepoints sent to printk,
|
|
echo 0 > /proc/sys/kernel/tracepoint_printk
|
|
Note, echoing 1 into this file without the
|
|
tracepoint_printk kernel cmdline option has no effect.
|
|
|
|
** CAUTION **
|
|
|
|
Having tracepoints sent to printk() and activating high
|
|
frequency tracepoints such as irq or sched, can cause
|
|
the system to live lock.
|
|
|
|
traceoff_on_warning
|
|
[FTRACE] enable this option to disable tracing when a
|
|
warning is hit. This turns off "tracing_on". Tracing can
|
|
be enabled again by echoing '1' into the "tracing_on"
|
|
file located in /sys/kernel/debug/tracing/
|
|
|
|
This option is useful, as it disables the trace before
|
|
the WARNING dump is called, which prevents the trace to
|
|
be filled with content caused by the warning output.
|
|
|
|
This option can also be set at run time via the sysctl
|
|
option: kernel/traceoff_on_warning
|
|
|
|
transparent_hugepage=
|
|
[KNL]
|
|
Format: [always|madvise|never]
|
|
Can be used to control the default behavior of the system
|
|
with respect to transparent hugepages.
|
|
See Documentation/admin-guide/mm/transhuge.rst
|
|
for more details.
|
|
|
|
trusted.source= [KEYS]
|
|
Format: <string>
|
|
This parameter identifies the trust source as a backend
|
|
for trusted keys implementation. Supported trust
|
|
sources:
|
|
- "tpm"
|
|
- "tee"
|
|
If not specified then it defaults to iterating through
|
|
the trust source list starting with TPM and assigns the
|
|
first trust source as a backend which is initialized
|
|
successfully during iteration.
|
|
|
|
tsc= Disable clocksource stability checks for TSC.
|
|
Format: <string>
|
|
[x86] reliable: mark tsc clocksource as reliable, this
|
|
disables clocksource verification at runtime, as well
|
|
as the stability checks done at bootup. Used to enable
|
|
high-resolution timer mode on older hardware, and in
|
|
virtualized environment.
|
|
[x86] noirqtime: Do not use TSC to do irq accounting.
|
|
Used to run time disable IRQ_TIME_ACCOUNTING on any
|
|
platforms where RDTSC is slow and this accounting
|
|
can add overhead.
|
|
[x86] unstable: mark the TSC clocksource as unstable, this
|
|
marks the TSC unconditionally unstable at bootup and
|
|
avoids any further wobbles once the TSC watchdog notices.
|
|
[x86] nowatchdog: disable clocksource watchdog. Used
|
|
in situations with strict latency requirements (where
|
|
interruptions from clocksource watchdog are not
|
|
acceptable).
|
|
|
|
tsc_early_khz= [X86] Skip early TSC calibration and use the given
|
|
value instead. Useful when the early TSC frequency discovery
|
|
procedure is not reliable, such as on overclocked systems
|
|
with CPUID.16h support and partial CPUID.15h support.
|
|
Format: <unsigned int>
|
|
|
|
tsx= [X86] Control Transactional Synchronization
|
|
Extensions (TSX) feature in Intel processors that
|
|
support TSX control.
|
|
|
|
This parameter controls the TSX feature. The options are:
|
|
|
|
on - Enable TSX on the system. Although there are
|
|
mitigations for all known security vulnerabilities,
|
|
TSX has been known to be an accelerator for
|
|
several previous speculation-related CVEs, and
|
|
so there may be unknown security risks associated
|
|
with leaving it enabled.
|
|
|
|
off - Disable TSX on the system. (Note that this
|
|
option takes effect only on newer CPUs which are
|
|
not vulnerable to MDS, i.e., have
|
|
MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 and which get
|
|
the new IA32_TSX_CTRL MSR through a microcode
|
|
update. This new MSR allows for the reliable
|
|
deactivation of the TSX functionality.)
|
|
|
|
auto - Disable TSX if X86_BUG_TAA is present,
|
|
otherwise enable TSX on the system.
|
|
|
|
Not specifying this option is equivalent to tsx=off.
|
|
|
|
See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
|
|
for more details.
|
|
|
|
tsx_async_abort= [X86,INTEL] Control mitigation for the TSX Async
|
|
Abort (TAA) vulnerability.
|
|
|
|
Similar to Micro-architectural Data Sampling (MDS)
|
|
certain CPUs that support Transactional
|
|
Synchronization Extensions (TSX) are vulnerable to an
|
|
exploit against CPU internal buffers which can forward
|
|
information to a disclosure gadget under certain
|
|
conditions.
|
|
|
|
In vulnerable processors, the speculatively forwarded
|
|
data can be used in a cache side channel attack, to
|
|
access data to which the attacker does not have direct
|
|
access.
|
|
|
|
This parameter controls the TAA mitigation. The
|
|
options are:
|
|
|
|
full - Enable TAA mitigation on vulnerable CPUs
|
|
if TSX is enabled.
|
|
|
|
full,nosmt - Enable TAA mitigation and disable SMT on
|
|
vulnerable CPUs. If TSX is disabled, SMT
|
|
is not disabled because CPU is not
|
|
vulnerable to cross-thread TAA attacks.
|
|
off - Unconditionally disable TAA mitigation
|
|
|
|
On MDS-affected machines, tsx_async_abort=off can be
|
|
prevented by an active MDS mitigation as both vulnerabilities
|
|
are mitigated with the same mechanism so in order to disable
|
|
this mitigation, you need to specify mds=off too.
|
|
|
|
Not specifying this option is equivalent to
|
|
tsx_async_abort=full. On CPUs which are MDS affected
|
|
and deploy MDS mitigation, TAA mitigation is not
|
|
required and doesn't provide any additional
|
|
mitigation.
|
|
|
|
For details see:
|
|
Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
|
|
|
|
turbografx.map[2|3]= [HW,JOY]
|
|
TurboGraFX parallel port interface
|
|
Format:
|
|
<port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
|
|
See also Documentation/input/devices/joystick-parport.rst
|
|
|
|
udbg-immortal [PPC] When debugging early kernel crashes that
|
|
happen after console_init() and before a proper
|
|
console driver takes over, this boot options might
|
|
help "seeing" what's going on.
|
|
|
|
uhash_entries= [KNL,NET]
|
|
Set number of hash buckets for UDP/UDP-Lite connections
|
|
|
|
uhci-hcd.ignore_oc=
|
|
[USB] Ignore overcurrent events (default N).
|
|
Some badly-designed motherboards generate lots of
|
|
bogus events, for ports that aren't wired to
|
|
anything. Set this parameter to avoid log spamming.
|
|
Note that genuine overcurrent events won't be
|
|
reported either.
|
|
|
|
unknown_nmi_panic
|
|
[X86] Cause panic on unknown NMI.
|
|
|
|
usbcore.authorized_default=
|
|
[USB] Default USB device authorization:
|
|
(default -1 = authorized except for wireless USB,
|
|
0 = not authorized, 1 = authorized, 2 = authorized
|
|
if device connected to internal port)
|
|
|
|
usbcore.autosuspend=
|
|
[USB] The autosuspend time delay (in seconds) used
|
|
for newly-detected USB devices (default 2). This
|
|
is the time required before an idle device will be
|
|
autosuspended. Devices for which the delay is set
|
|
to a negative value won't be autosuspended at all.
|
|
|
|
usbcore.usbfs_snoop=
|
|
[USB] Set to log all usbfs traffic (default 0 = off).
|
|
|
|
usbcore.usbfs_snoop_max=
|
|
[USB] Maximum number of bytes to snoop in each URB
|
|
(default = 65536).
|
|
|
|
usbcore.blinkenlights=
|
|
[USB] Set to cycle leds on hubs (default 0 = off).
|
|
|
|
usbcore.old_scheme_first=
|
|
[USB] Start with the old device initialization
|
|
scheme (default 0 = off).
|
|
|
|
usbcore.usbfs_memory_mb=
|
|
[USB] Memory limit (in MB) for buffers allocated by
|
|
usbfs (default = 16, 0 = max = 2047).
|
|
|
|
usbcore.use_both_schemes=
|
|
[USB] Try the other device initialization scheme
|
|
if the first one fails (default 1 = enabled).
|
|
|
|
usbcore.initial_descriptor_timeout=
|
|
[USB] Specifies timeout for the initial 64-byte
|
|
USB_REQ_GET_DESCRIPTOR request in milliseconds
|
|
(default 5000 = 5.0 seconds).
|
|
|
|
usbcore.nousb [USB] Disable the USB subsystem
|
|
|
|
usbcore.quirks=
|
|
[USB] A list of quirk entries to augment the built-in
|
|
usb core quirk list. List entries are separated by
|
|
commas. Each entry has the form
|
|
VendorID:ProductID:Flags. The IDs are 4-digit hex
|
|
numbers and Flags is a set of letters. Each letter
|
|
will change the built-in quirk; setting it if it is
|
|
clear and clearing it if it is set. The letters have
|
|
the following meanings:
|
|
a = USB_QUIRK_STRING_FETCH_255 (string
|
|
descriptors must not be fetched using
|
|
a 255-byte read);
|
|
b = USB_QUIRK_RESET_RESUME (device can't resume
|
|
correctly so reset it instead);
|
|
c = USB_QUIRK_NO_SET_INTF (device can't handle
|
|
Set-Interface requests);
|
|
d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
|
|
handle its Configuration or Interface
|
|
strings);
|
|
e = USB_QUIRK_RESET (device can't be reset
|
|
(e.g morph devices), don't use reset);
|
|
f = USB_QUIRK_HONOR_BNUMINTERFACES (device has
|
|
more interface descriptions than the
|
|
bNumInterfaces count, and can't handle
|
|
talking to these interfaces);
|
|
g = USB_QUIRK_DELAY_INIT (device needs a pause
|
|
during initialization, after we read
|
|
the device descriptor);
|
|
h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For
|
|
high speed and super speed interrupt
|
|
endpoints, the USB 2.0 and USB 3.0 spec
|
|
require the interval in microframes (1
|
|
microframe = 125 microseconds) to be
|
|
calculated as interval = 2 ^
|
|
(bInterval-1).
|
|
Devices with this quirk report their
|
|
bInterval as the result of this
|
|
calculation instead of the exponent
|
|
variable used in the calculation);
|
|
i = USB_QUIRK_DEVICE_QUALIFIER (device can't
|
|
handle device_qualifier descriptor
|
|
requests);
|
|
j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device
|
|
generates spurious wakeup, ignore
|
|
remote wakeup capability);
|
|
k = USB_QUIRK_NO_LPM (device can't handle Link
|
|
Power Management);
|
|
l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL
|
|
(Device reports its bInterval as linear
|
|
frames instead of the USB 2.0
|
|
calculation);
|
|
m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs
|
|
to be disconnected before suspend to
|
|
prevent spurious wakeup);
|
|
n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a
|
|
pause after every control message);
|
|
o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra
|
|
delay after resetting its port);
|
|
Example: quirks=0781:5580:bk,0a5c:5834:gij
|
|
|
|
usbhid.mousepoll=
|
|
[USBHID] The interval which mice are to be polled at.
|
|
|
|
usbhid.jspoll=
|
|
[USBHID] The interval which joysticks are to be polled at.
|
|
|
|
usbhid.kbpoll=
|
|
[USBHID] The interval which keyboards are to be polled at.
|
|
|
|
usb-storage.delay_use=
|
|
[UMS] The delay in seconds before a new device is
|
|
scanned for Logical Units (default 1).
|
|
|
|
usb-storage.quirks=
|
|
[UMS] A list of quirks entries to supplement or
|
|
override the built-in unusual_devs list. List
|
|
entries are separated by commas. Each entry has
|
|
the form VID:PID:Flags where VID and PID are Vendor
|
|
and Product ID values (4-digit hex numbers) and
|
|
Flags is a set of characters, each corresponding
|
|
to a common usb-storage quirk flag as follows:
|
|
a = SANE_SENSE (collect more than 18 bytes
|
|
of sense data, not on uas);
|
|
b = BAD_SENSE (don't collect more than 18
|
|
bytes of sense data, not on uas);
|
|
c = FIX_CAPACITY (decrease the reported
|
|
device capacity by one sector);
|
|
d = NO_READ_DISC_INFO (don't use
|
|
READ_DISC_INFO command, not on uas);
|
|
e = NO_READ_CAPACITY_16 (don't use
|
|
READ_CAPACITY_16 command);
|
|
f = NO_REPORT_OPCODES (don't use report opcodes
|
|
command, uas only);
|
|
g = MAX_SECTORS_240 (don't transfer more than
|
|
240 sectors at a time, uas only);
|
|
h = CAPACITY_HEURISTICS (decrease the
|
|
reported device capacity by one
|
|
sector if the number is odd);
|
|
i = IGNORE_DEVICE (don't bind to this
|
|
device);
|
|
j = NO_REPORT_LUNS (don't use report luns
|
|
command, uas only);
|
|
k = NO_SAME (do not use WRITE_SAME, uas only)
|
|
l = NOT_LOCKABLE (don't try to lock and
|
|
unlock ejectable media, not on uas);
|
|
m = MAX_SECTORS_64 (don't transfer more
|
|
than 64 sectors = 32 KB at a time,
|
|
not on uas);
|
|
n = INITIAL_READ10 (force a retry of the
|
|
initial READ(10) command, not on uas);
|
|
o = CAPACITY_OK (accept the capacity
|
|
reported by the device, not on uas);
|
|
p = WRITE_CACHE (the device cache is ON
|
|
by default, not on uas);
|
|
r = IGNORE_RESIDUE (the device reports
|
|
bogus residue values, not on uas);
|
|
s = SINGLE_LUN (the device has only one
|
|
Logical Unit);
|
|
t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
|
|
commands, uas only);
|
|
u = IGNORE_UAS (don't bind to the uas driver);
|
|
w = NO_WP_DETECT (don't test whether the
|
|
medium is write-protected).
|
|
y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
|
|
even if the device claims no cache,
|
|
not on uas)
|
|
Example: quirks=0419:aaf5:rl,0421:0433:rc
|
|
|
|
user_debug= [KNL,ARM]
|
|
Format: <int>
|
|
See arch/arm/Kconfig.debug help text.
|
|
1 - undefined instruction events
|
|
2 - system calls
|
|
4 - invalid data aborts
|
|
8 - SIGSEGV faults
|
|
16 - SIGBUS faults
|
|
Example: user_debug=31
|
|
|
|
userpte=
|
|
[X86] Flags controlling user PTE allocations.
|
|
|
|
nohigh = do not allocate PTE pages in
|
|
HIGHMEM regardless of setting
|
|
of CONFIG_HIGHPTE.
|
|
|
|
vdso= [X86,SH]
|
|
On X86_32, this is an alias for vdso32=. Otherwise:
|
|
|
|
vdso=1: enable VDSO (the default)
|
|
vdso=0: disable VDSO mapping
|
|
|
|
vdso32= [X86] Control the 32-bit vDSO
|
|
vdso32=1: enable 32-bit VDSO
|
|
vdso32=0 or vdso32=2: disable 32-bit VDSO
|
|
|
|
See the help text for CONFIG_COMPAT_VDSO for more
|
|
details. If CONFIG_COMPAT_VDSO is set, the default is
|
|
vdso32=0; otherwise, the default is vdso32=1.
|
|
|
|
For compatibility with older kernels, vdso32=2 is an
|
|
alias for vdso32=0.
|
|
|
|
Try vdso32=0 if you encounter an error that says:
|
|
dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
|
|
|
|
vector= [IA-64,SMP]
|
|
vector=percpu: enable percpu vector domain
|
|
|
|
video= [FB] Frame buffer configuration
|
|
See Documentation/fb/modedb.rst.
|
|
|
|
video.brightness_switch_enabled= [0,1]
|
|
If set to 1, on receiving an ACPI notify event
|
|
generated by hotkey, video driver will adjust brightness
|
|
level and then send out the event to user space through
|
|
the allocated input device; If set to 0, video driver
|
|
will only send out the event without touching backlight
|
|
brightness level.
|
|
default: 1
|
|
|
|
virtio_mmio.device=
|
|
[VMMIO] Memory mapped virtio (platform) device.
|
|
|
|
<size>@<baseaddr>:<irq>[:<id>]
|
|
where:
|
|
<size> := size (can use standard suffixes
|
|
like K, M and G)
|
|
<baseaddr> := physical base address
|
|
<irq> := interrupt number (as passed to
|
|
request_irq())
|
|
<id> := (optional) platform device id
|
|
example:
|
|
virtio_mmio.device=1K@0x100b0000:48:7
|
|
|
|
Can be used multiple times for multiple devices.
|
|
|
|
vga= [BOOT,X86-32] Select a particular video mode
|
|
See Documentation/x86/boot.rst and
|
|
Documentation/admin-guide/svga.rst.
|
|
Use vga=ask for menu.
|
|
This is actually a boot loader parameter; the value is
|
|
passed to the kernel using a special protocol.
|
|
|
|
vm_debug[=options] [KNL] Available with CONFIG_DEBUG_VM=y.
|
|
May slow down system boot speed, especially when
|
|
enabled on systems with a large amount of memory.
|
|
All options are enabled by default, and this
|
|
interface is meant to allow for selectively
|
|
enabling or disabling specific virtual memory
|
|
debugging features.
|
|
|
|
Available options are:
|
|
P Enable page structure init time poisoning
|
|
- Disable all of the above options
|
|
|
|
vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
|
|
size of <nn>. This can be used to increase the
|
|
minimum size (128MB on x86). It can also be used to
|
|
decrease the size and leave more room for directly
|
|
mapped kernel RAM.
|
|
|
|
vmcp_cma=nn[MG] [KNL,S390]
|
|
Sets the memory size reserved for contiguous memory
|
|
allocations for the vmcp device driver.
|
|
|
|
vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
|
|
Format: <command>
|
|
|
|
vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
|
|
Format: <command>
|
|
|
|
vmpoff= [KNL,S390] Perform z/VM CP command after power off.
|
|
Format: <command>
|
|
|
|
vsyscall= [X86-64]
|
|
Controls the behavior of vsyscalls (i.e. calls to
|
|
fixed addresses of 0xffffffffff600x00 from legacy
|
|
code). Most statically-linked binaries and older
|
|
versions of glibc use these calls. Because these
|
|
functions are at fixed addresses, they make nice
|
|
targets for exploits that can control RIP.
|
|
|
|
emulate [default] Vsyscalls turn into traps and are
|
|
emulated reasonably safely. The vsyscall
|
|
page is readable.
|
|
|
|
xonly Vsyscalls turn into traps and are
|
|
emulated reasonably safely. The vsyscall
|
|
page is not readable.
|
|
|
|
none Vsyscalls don't work at all. This makes
|
|
them quite hard to use for exploits but
|
|
might break your system.
|
|
|
|
vt.color= [VT] Default text color.
|
|
Format: 0xYX, X = foreground, Y = background.
|
|
Default: 0x07 = light gray on black.
|
|
|
|
vt.cur_default= [VT] Default cursor shape.
|
|
Format: 0xCCBBAA, where AA, BB, and CC are the same as
|
|
the parameters of the <Esc>[?A;B;Cc escape sequence;
|
|
see VGA-softcursor.txt. Default: 2 = underline.
|
|
|
|
vt.default_blu= [VT]
|
|
Format: <blue0>,<blue1>,<blue2>,...,<blue15>
|
|
Change the default blue palette of the console.
|
|
This is a 16-member array composed of values
|
|
ranging from 0-255.
|
|
|
|
vt.default_grn= [VT]
|
|
Format: <green0>,<green1>,<green2>,...,<green15>
|
|
Change the default green palette of the console.
|
|
This is a 16-member array composed of values
|
|
ranging from 0-255.
|
|
|
|
vt.default_red= [VT]
|
|
Format: <red0>,<red1>,<red2>,...,<red15>
|
|
Change the default red palette of the console.
|
|
This is a 16-member array composed of values
|
|
ranging from 0-255.
|
|
|
|
vt.default_utf8=
|
|
[VT]
|
|
Format=<0|1>
|
|
Set system-wide default UTF-8 mode for all tty's.
|
|
Default is 1, i.e. UTF-8 mode is enabled for all
|
|
newly opened terminals.
|
|
|
|
vt.global_cursor_default=
|
|
[VT]
|
|
Format=<-1|0|1>
|
|
Set system-wide default for whether a cursor
|
|
is shown on new VTs. Default is -1,
|
|
i.e. cursors will be created by default unless
|
|
overridden by individual drivers. 0 will hide
|
|
cursors, 1 will display them.
|
|
|
|
vt.italic= [VT] Default color for italic text; 0-15.
|
|
Default: 2 = green.
|
|
|
|
vt.underline= [VT] Default color for underlined text; 0-15.
|
|
Default: 3 = cyan.
|
|
|
|
watchdog timers [HW,WDT] For information on watchdog timers,
|
|
see Documentation/watchdog/watchdog-parameters.rst
|
|
or other driver-specific files in the
|
|
Documentation/watchdog/ directory.
|
|
|
|
watchdog_thresh=
|
|
[KNL]
|
|
Set the hard lockup detector stall duration
|
|
threshold in seconds. The soft lockup detector
|
|
threshold is set to twice the value. A value of 0
|
|
disables both lockup detectors. Default is 10
|
|
seconds.
|
|
|
|
workqueue.watchdog_thresh=
|
|
If CONFIG_WQ_WATCHDOG is configured, workqueue can
|
|
warn stall conditions and dump internal state to
|
|
help debugging. 0 disables workqueue stall
|
|
detection; otherwise, it's the stall threshold
|
|
duration in seconds. The default value is 30 and
|
|
it can be updated at runtime by writing to the
|
|
corresponding sysfs file.
|
|
|
|
workqueue.disable_numa
|
|
By default, all work items queued to unbound
|
|
workqueues are affine to the NUMA nodes they're
|
|
issued on, which results in better behavior in
|
|
general. If NUMA affinity needs to be disabled for
|
|
whatever reason, this option can be used. Note
|
|
that this also can be controlled per-workqueue for
|
|
workqueues visible under /sys/bus/workqueue/.
|
|
|
|
workqueue.power_efficient
|
|
Per-cpu workqueues are generally preferred because
|
|
they show better performance thanks to cache
|
|
locality; unfortunately, per-cpu workqueues tend to
|
|
be more power hungry than unbound workqueues.
|
|
|
|
Enabling this makes the per-cpu workqueues which
|
|
were observed to contribute significantly to power
|
|
consumption unbound, leading to measurably lower
|
|
power usage at the cost of small performance
|
|
overhead.
|
|
|
|
The default value of this parameter is determined by
|
|
the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
|
|
|
|
workqueue.debug_force_rr_cpu
|
|
Workqueue used to implicitly guarantee that work
|
|
items queued without explicit CPU specified are put
|
|
on the local CPU. This guarantee is no longer true
|
|
and while local CPU is still preferred work items
|
|
may be put on foreign CPUs. This debug option
|
|
forces round-robin CPU selection to flush out
|
|
usages which depend on the now broken guarantee.
|
|
When enabled, memory and cache locality will be
|
|
impacted.
|
|
|
|
x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
|
|
default x2apic cluster mode on platforms
|
|
supporting x2apic.
|
|
|
|
xen_512gb_limit [KNL,X86-64,XEN]
|
|
Restricts the kernel running paravirtualized under Xen
|
|
to use only up to 512 GB of RAM. The reason to do so is
|
|
crash analysis tools and Xen tools for doing domain
|
|
save/restore/migration must be enabled to handle larger
|
|
domains.
|
|
|
|
xen_emul_unplug= [HW,X86,XEN]
|
|
Unplug Xen emulated devices
|
|
Format: [unplug0,][unplug1]
|
|
ide-disks -- unplug primary master IDE devices
|
|
aux-ide-disks -- unplug non-primary-master IDE devices
|
|
nics -- unplug network devices
|
|
all -- unplug all emulated devices (NICs and IDE disks)
|
|
unnecessary -- unplugging emulated devices is
|
|
unnecessary even if the host did not respond to
|
|
the unplug protocol
|
|
never -- do not unplug even if version check succeeds
|
|
|
|
xen_legacy_crash [X86,XEN]
|
|
Crash from Xen panic notifier, without executing late
|
|
panic() code such as dumping handler.
|
|
|
|
xen_nopvspin [X86,XEN]
|
|
Disables the qspinlock slowpath using Xen PV optimizations.
|
|
This parameter is obsoleted by "nopvspin" parameter, which
|
|
has equivalent effect for XEN platform.
|
|
|
|
xen_nopv [X86]
|
|
Disables the PV optimizations forcing the HVM guest to
|
|
run as generic HVM guest with no PV drivers.
|
|
This option is obsoleted by the "nopv" option, which
|
|
has equivalent effect for XEN platform.
|
|
|
|
xen_no_vector_callback
|
|
[KNL,X86,XEN] Disable the vector callback for Xen
|
|
event channel interrupts.
|
|
|
|
xen_scrub_pages= [XEN]
|
|
Boolean option to control scrubbing pages before giving them back
|
|
to Xen, for use by other domains. Can be also changed at runtime
|
|
with /sys/devices/system/xen_memory/xen_memory0/scrub_pages.
|
|
Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT.
|
|
|
|
xen_timer_slop= [X86-64,XEN]
|
|
Set the timer slop (in nanoseconds) for the virtual Xen
|
|
timers (default is 100000). This adjusts the minimum
|
|
delta of virtualized Xen timers, where lower values
|
|
improve timer resolution at the expense of processing
|
|
more timer interrupts.
|
|
|
|
xen.event_eoi_delay= [XEN]
|
|
How long to delay EOI handling in case of event
|
|
storms (jiffies). Default is 10.
|
|
|
|
xen.event_loop_timeout= [XEN]
|
|
After which time (jiffies) the event handling loop
|
|
should start to delay EOI handling. Default is 2.
|
|
|
|
xen.fifo_events= [XEN]
|
|
Boolean parameter to disable using fifo event handling
|
|
even if available. Normally fifo event handling is
|
|
preferred over the 2-level event handling, as it is
|
|
fairer and the number of possible event channels is
|
|
much higher. Default is on (use fifo events).
|
|
|
|
nopv= [X86,XEN,KVM,HYPER_V,VMWARE]
|
|
Disables the PV optimizations forcing the guest to run
|
|
as generic guest with no PV drivers. Currently support
|
|
XEN HVM, KVM, HYPER_V and VMWARE guest.
|
|
|
|
nopvspin [X86,XEN,KVM]
|
|
Disables the qspinlock slow path using PV optimizations
|
|
which allow the hypervisor to 'idle' the guest on lock
|
|
contention.
|
|
|
|
xirc2ps_cs= [NET,PCMCIA]
|
|
Format:
|
|
<irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
|
|
|
|
xive= [PPC]
|
|
By default on POWER9 and above, the kernel will
|
|
natively use the XIVE interrupt controller. This option
|
|
allows the fallback firmware mode to be used:
|
|
|
|
off Fallback to firmware control of XIVE interrupt
|
|
controller on both pseries and powernv
|
|
platforms. Only useful on POWER9 and above.
|
|
|
|
xhci-hcd.quirks [USB,KNL]
|
|
A hex value specifying bitmask with supplemental xhci
|
|
host controller quirks. Meaning of each bit can be
|
|
consulted in header drivers/usb/host/xhci.h.
|
|
|
|
xmon [PPC]
|
|
Format: { early | on | rw | ro | off }
|
|
Controls if xmon debugger is enabled. Default is off.
|
|
Passing only "xmon" is equivalent to "xmon=early".
|
|
early Call xmon as early as possible on boot; xmon
|
|
debugger is called from setup_arch().
|
|
on xmon debugger hooks will be installed so xmon
|
|
is only called on a kernel crash. Default mode,
|
|
i.e. either "ro" or "rw" mode, is controlled
|
|
with CONFIG_XMON_DEFAULT_RO_MODE.
|
|
rw xmon debugger hooks will be installed so xmon
|
|
is called only on a kernel crash, mode is write,
|
|
meaning SPR registers, memory and, other data
|
|
can be written using xmon commands.
|
|
ro same as "rw" option above but SPR registers,
|
|
memory, and other data can't be written using
|
|
xmon commands.
|
|
off xmon is disabled.
|