308 lines
12 KiB
Plaintext
308 lines
12 KiB
Plaintext
AMD64 specific boot options
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There are many others (usually documented in driver documentation), but
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only the AMD64 specific ones are listed here.
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Machine check
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mce=off disable machine check
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mce=bootlog Enable logging of machine checks left over from booting.
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Disabled by default on AMD because some BIOS leave bogus ones.
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If your BIOS doesn't do that it's a good idea to enable though
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to make sure you log even machine check events that result
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in a reboot. On Intel systems it is enabled by default.
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mce=nobootlog
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Disable boot machine check logging.
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mce=tolerancelevel (number)
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0: always panic, 1: panic if deadlock possible,
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2: try to avoid panic, 3: never panic or exit (for testing)
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default is 1
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Can be also set using sysfs which is preferable.
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nomce (for compatibility with i386): same as mce=off
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Everything else is in sysfs now.
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APICs
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apic Use IO-APIC. Default
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noapic Don't use the IO-APIC.
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disableapic Don't use the local APIC
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nolapic Don't use the local APIC (alias for i386 compatibility)
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pirq=... See Documentation/i386/IO-APIC.txt
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noapictimer Don't set up the APIC timer
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no_timer_check Don't check the IO-APIC timer. This can work around
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problems with incorrect timer initialization on some boards.
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apicmaintimer Run time keeping from the local APIC timer instead
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of using the PIT/HPET interrupt for this. This is useful
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when the PIT/HPET interrupts are unreliable.
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noapicmaintimer Don't do time keeping using the APIC timer.
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Useful when this option was auto selected, but doesn't work.
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apicpmtimer
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Do APIC timer calibration using the pmtimer. Implies
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apicmaintimer. Useful when your PIT timer is totally
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broken.
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disable_8254_timer / enable_8254_timer
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Enable interrupt 0 timer routing over the 8254 in addition to over
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the IO-APIC. The kernel tries to set a sensible default.
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Early Console
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syntax: earlyprintk=vga
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earlyprintk=serial[,ttySn[,baudrate]]
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The early console is useful when the kernel crashes before the
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normal console is initialized. It is not enabled by
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default because it has some cosmetic problems.
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Append ,keep to not disable it when the real console takes over.
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Only vga or serial at a time, not both.
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Currently only ttyS0 and ttyS1 are supported.
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Interaction with the standard serial driver is not very good.
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The VGA output is eventually overwritten by the real console.
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Timing
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notsc
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Don't use the CPU time stamp counter to read the wall time.
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This can be used to work around timing problems on multiprocessor systems
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with not properly synchronized CPUs.
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report_lost_ticks
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Report when timer interrupts are lost because some code turned off
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interrupts for too long.
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nmi_watchdog=NUMBER[,panic]
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NUMBER can be:
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0 don't use an NMI watchdog
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1 use the IO-APIC timer for the NMI watchdog
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2 use the local APIC for the NMI watchdog using a performance counter. Note
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This will use one performance counter and the local APIC's performance
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vector.
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When panic is specified panic when an NMI watchdog timeout occurs.
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This is useful when you use a panic=... timeout and need the box
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quickly up again.
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nohpet
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Don't use the HPET timer.
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Idle loop
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idle=poll
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Don't do power saving in the idle loop using HLT, but poll for rescheduling
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event. This will make the CPUs eat a lot more power, but may be useful
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to get slightly better performance in multiprocessor benchmarks. It also
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makes some profiling using performance counters more accurate.
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Please note that on systems with MONITOR/MWAIT support (like Intel EM64T
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CPUs) this option has no performance advantage over the normal idle loop.
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It may also interact badly with hyperthreading.
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Rebooting
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reboot=b[ios] | t[riple] | k[bd] [, [w]arm | [c]old]
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bios Use the CPU reboot vector for warm reset
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warm Don't set the cold reboot flag
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cold Set the cold reboot flag
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triple Force a triple fault (init)
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kbd Use the keyboard controller. cold reset (default)
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Using warm reset will be much faster especially on big memory
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systems because the BIOS will not go through the memory check.
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Disadvantage is that not all hardware will be completely reinitialized
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on reboot so there may be boot problems on some systems.
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reboot=force
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Don't stop other CPUs on reboot. This can make reboot more reliable
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in some cases.
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Non Executable Mappings
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noexec=on|off
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on Enable(default)
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off Disable
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SMP
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nosmp Only use a single CPU
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maxcpus=NUMBER only use upto NUMBER CPUs
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cpumask=MASK only use cpus with bits set in mask
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additional_cpus=NUM Allow NUM more CPUs for hotplug
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(defaults are specified by the BIOS, see Documentation/x86_64/cpu-hotplug-spec)
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NUMA
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numa=off Only set up a single NUMA node spanning all memory.
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numa=noacpi Don't parse the SRAT table for NUMA setup
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numa=fake=CMDLINE
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If a number, fakes CMDLINE nodes and ignores NUMA setup of the
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actual machine. Otherwise, system memory is configured
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depending on the sizes and coefficients listed. For example:
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numa=fake=2*512,1024,4*256,*128
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gives two 512M nodes, a 1024M node, four 256M nodes, and the
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rest split into 128M chunks. If the last character of CMDLINE
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is a *, the remaining memory is divided up equally among its
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coefficient:
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numa=fake=2*512,2*
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gives two 512M nodes and the rest split into two nodes.
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Otherwise, the remaining system RAM is allocated to an
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additional node.
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numa=hotadd=percent
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Only allow hotadd memory to preallocate page structures upto
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percent of already available memory.
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numa=hotadd=0 will disable hotadd memory.
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ACPI
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acpi=off Don't enable ACPI
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acpi=ht Use ACPI boot table parsing, but don't enable ACPI
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interpreter
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acpi=force Force ACPI on (currently not needed)
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acpi=strict Disable out of spec ACPI workarounds.
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acpi_sci={edge,level,high,low} Set up ACPI SCI interrupt.
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acpi=noirq Don't route interrupts
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PCI
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pci=off Don't use PCI
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pci=conf1 Use conf1 access.
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pci=conf2 Use conf2 access.
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pci=rom Assign ROMs.
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pci=assign-busses Assign busses
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pci=irqmask=MASK Set PCI interrupt mask to MASK
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pci=lastbus=NUMBER Scan upto NUMBER busses, no matter what the mptable says.
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pci=noacpi Don't use ACPI to set up PCI interrupt routing.
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IOMMU (input/output memory management unit)
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Currently four x86-64 PCI-DMA mapping implementations exist:
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1. <arch/x86_64/kernel/pci-nommu.c>: use no hardware/software IOMMU at all
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(e.g. because you have < 3 GB memory).
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Kernel boot message: "PCI-DMA: Disabling IOMMU"
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2. <arch/x86_64/kernel/pci-gart.c>: AMD GART based hardware IOMMU.
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Kernel boot message: "PCI-DMA: using GART IOMMU"
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3. <arch/x86_64/kernel/pci-swiotlb.c> : Software IOMMU implementation. Used
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e.g. if there is no hardware IOMMU in the system and it is need because
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you have >3GB memory or told the kernel to us it (iommu=soft))
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Kernel boot message: "PCI-DMA: Using software bounce buffering
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for IO (SWIOTLB)"
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4. <arch/x86_64/pci-calgary.c> : IBM Calgary hardware IOMMU. Used in IBM
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pSeries and xSeries servers. This hardware IOMMU supports DMA address
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mapping with memory protection, etc.
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Kernel boot message: "PCI-DMA: Using Calgary IOMMU"
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iommu=[<size>][,noagp][,off][,force][,noforce][,leak[=<nr_of_leak_pages>]
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[,memaper[=<order>]][,merge][,forcesac][,fullflush][,nomerge]
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[,noaperture][,calgary]
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General iommu options:
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off Don't initialize and use any kind of IOMMU.
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noforce Don't force hardware IOMMU usage when it is not needed.
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(default).
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force Force the use of the hardware IOMMU even when it is
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not actually needed (e.g. because < 3 GB memory).
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soft Use software bounce buffering (SWIOTLB) (default for
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Intel machines). This can be used to prevent the usage
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of an available hardware IOMMU.
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iommu options only relevant to the AMD GART hardware IOMMU:
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<size> Set the size of the remapping area in bytes.
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allowed Overwrite iommu off workarounds for specific chipsets.
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fullflush Flush IOMMU on each allocation (default).
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nofullflush Don't use IOMMU fullflush.
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leak Turn on simple iommu leak tracing (only when
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CONFIG_IOMMU_LEAK is on). Default number of leak pages
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is 20.
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memaper[=<order>] Allocate an own aperture over RAM with size 32MB<<order.
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(default: order=1, i.e. 64MB)
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merge Do scatter-gather (SG) merging. Implies "force"
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(experimental).
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nomerge Don't do scatter-gather (SG) merging.
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noaperture Ask the IOMMU not to touch the aperture for AGP.
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forcesac Force single-address cycle (SAC) mode for masks <40bits
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(experimental).
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noagp Don't initialize the AGP driver and use full aperture.
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allowdac Allow double-address cycle (DAC) mode, i.e. DMA >4GB.
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DAC is used with 32-bit PCI to push a 64-bit address in
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two cycles. When off all DMA over >4GB is forced through
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an IOMMU or software bounce buffering.
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nodac Forbid DAC mode, i.e. DMA >4GB.
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panic Always panic when IOMMU overflows.
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calgary Use the Calgary IOMMU if it is available
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iommu options only relevant to the software bounce buffering (SWIOTLB) IOMMU
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implementation:
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swiotlb=<pages>[,force]
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<pages> Prereserve that many 128K pages for the software IO
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bounce buffering.
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force Force all IO through the software TLB.
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Settings for the IBM Calgary hardware IOMMU currently found in IBM
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pSeries and xSeries machines:
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calgary=[64k,128k,256k,512k,1M,2M,4M,8M]
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calgary=[translate_empty_slots]
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calgary=[disable=<PCI bus number>]
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panic Always panic when IOMMU overflows
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64k,...,8M - Set the size of each PCI slot's translation table
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when using the Calgary IOMMU. This is the size of the translation
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table itself in main memory. The smallest table, 64k, covers an IO
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space of 32MB; the largest, 8MB table, can cover an IO space of
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4GB. Normally the kernel will make the right choice by itself.
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translate_empty_slots - Enable translation even on slots that have
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no devices attached to them, in case a device will be hotplugged
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in the future.
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disable=<PCI bus number> - Disable translation on a given PHB. For
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example, the built-in graphics adapter resides on the first bridge
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(PCI bus number 0); if translation (isolation) is enabled on this
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bridge, X servers that access the hardware directly from user
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space might stop working. Use this option if you have devices that
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are accessed from userspace directly on some PCI host bridge.
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Debugging
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oops=panic Always panic on oopses. Default is to just kill the process,
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but there is a small probability of deadlocking the machine.
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This will also cause panics on machine check exceptions.
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Useful together with panic=30 to trigger a reboot.
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kstack=N Print N words from the kernel stack in oops dumps.
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pagefaulttrace Dump all page faults. Only useful for extreme debugging
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and will create a lot of output.
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call_trace=[old|both|newfallback|new]
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old: use old inexact backtracer
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new: use new exact dwarf2 unwinder
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both: print entries from both
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newfallback: use new unwinder but fall back to old if it gets
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stuck (default)
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Miscellaneous
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