docs: virt: Convert msr.txt to ReST format
- Use document title markup; - Convert tables; - Add blank lines and adjust indentation. Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Mauro Carvalho Chehab
Paolo Bonzini
parent
2756df60d0
commit
263a19ff21
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@ -10,6 +10,7 @@ KVM
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amd-memory-encryption
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cpuid
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halt-polling
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msr
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vcpu-requests
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arm/index
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@ -1,6 +1,10 @@
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KVM-specific MSRs.
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Glauber Costa <glommer@redhat.com>, Red Hat Inc, 2010
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=====================================================
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.. SPDX-License-Identifier: GPL-2.0
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=================
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KVM-specific MSRs
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=================
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:Author: Glauber Costa <glommer@redhat.com>, Red Hat Inc, 2010
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KVM makes use of some custom MSRs to service some requests.
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@ -9,34 +13,39 @@ Custom MSRs have a range reserved for them, that goes from
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but they are deprecated and their use is discouraged.
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Custom MSR list
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--------
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---------------
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The current supported Custom MSR list is:
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MSR_KVM_WALL_CLOCK_NEW: 0x4b564d00
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MSR_KVM_WALL_CLOCK_NEW:
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0x4b564d00
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data: 4-byte alignment physical address of a memory area which must be
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data:
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4-byte alignment physical address of a memory area which must be
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in guest RAM. This memory is expected to hold a copy of the following
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structure:
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structure::
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struct pvclock_wall_clock {
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struct pvclock_wall_clock {
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u32 version;
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u32 sec;
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u32 nsec;
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} __attribute__((__packed__));
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} __attribute__((__packed__));
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whose data will be filled in by the hypervisor. The hypervisor is only
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guaranteed to update this data at the moment of MSR write.
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Users that want to reliably query this information more than once have
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to write more than once to this MSR. Fields have the following meanings:
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version: guest has to check version before and after grabbing
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version:
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guest has to check version before and after grabbing
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time information and check that they are both equal and even.
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An odd version indicates an in-progress update.
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sec: number of seconds for wallclock at time of boot.
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sec:
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number of seconds for wallclock at time of boot.
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nsec: number of nanoseconds for wallclock at time of boot.
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nsec:
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number of nanoseconds for wallclock at time of boot.
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In order to get the current wallclock time, the system_time from
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MSR_KVM_SYSTEM_TIME_NEW needs to be added.
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@ -47,13 +56,15 @@ MSR_KVM_WALL_CLOCK_NEW: 0x4b564d00
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Availability of this MSR must be checked via bit 3 in 0x4000001 cpuid
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leaf prior to usage.
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MSR_KVM_SYSTEM_TIME_NEW: 0x4b564d01
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MSR_KVM_SYSTEM_TIME_NEW:
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0x4b564d01
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data: 4-byte aligned physical address of a memory area which must be in
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data:
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4-byte aligned physical address of a memory area which must be in
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guest RAM, plus an enable bit in bit 0. This memory is expected to hold
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a copy of the following structure:
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a copy of the following structure::
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struct pvclock_vcpu_time_info {
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struct pvclock_vcpu_time_info {
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u32 version;
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u32 pad0;
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u64 tsc_timestamp;
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@ -62,7 +73,7 @@ MSR_KVM_SYSTEM_TIME_NEW: 0x4b564d01
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s8 tsc_shift;
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u8 flags;
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u8 pad[2];
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} __attribute__((__packed__)); /* 32 bytes */
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} __attribute__((__packed__)); /* 32 bytes */
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whose data will be filled in by the hypervisor periodically. Only one
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write, or registration, is needed for each VCPU. The interval between
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@ -72,23 +83,28 @@ MSR_KVM_SYSTEM_TIME_NEW: 0x4b564d01
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Fields have the following meanings:
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version: guest has to check version before and after grabbing
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version:
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guest has to check version before and after grabbing
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time information and check that they are both equal and even.
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An odd version indicates an in-progress update.
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tsc_timestamp: the tsc value at the current VCPU at the time
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tsc_timestamp:
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the tsc value at the current VCPU at the time
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of the update of this structure. Guests can subtract this value
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from current tsc to derive a notion of elapsed time since the
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structure update.
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system_time: a host notion of monotonic time, including sleep
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system_time:
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a host notion of monotonic time, including sleep
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time at the time this structure was last updated. Unit is
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nanoseconds.
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tsc_to_system_mul: multiplier to be used when converting
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tsc_to_system_mul:
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multiplier to be used when converting
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tsc-related quantity to nanoseconds
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tsc_shift: shift to be used when converting tsc-related
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tsc_shift:
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shift to be used when converting tsc-related
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quantity to nanoseconds. This shift will ensure that
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multiplication with tsc_to_system_mul does not overflow.
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A positive value denotes a left shift, a negative value
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@ -96,7 +112,7 @@ MSR_KVM_SYSTEM_TIME_NEW: 0x4b564d01
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The conversion from tsc to nanoseconds involves an additional
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right shift by 32 bits. With this information, guests can
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derive per-CPU time by doing:
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derive per-CPU time by doing::
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time = (current_tsc - tsc_timestamp)
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if (tsc_shift >= 0)
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@ -106,29 +122,34 @@ MSR_KVM_SYSTEM_TIME_NEW: 0x4b564d01
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time = (time * tsc_to_system_mul) >> 32
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time = time + system_time
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flags: bits in this field indicate extended capabilities
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flags:
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bits in this field indicate extended capabilities
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coordinated between the guest and the hypervisor. Availability
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of specific flags has to be checked in 0x40000001 cpuid leaf.
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Current flags are:
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flag bit | cpuid bit | meaning
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-------------------------------------------------------------
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| | time measures taken across
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0 | 24 | multiple cpus are guaranteed to
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| | be monotonic
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-------------------------------------------------------------
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| | guest vcpu has been paused by
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1 | N/A | the host
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| | See 4.70 in api.txt
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-------------------------------------------------------------
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+-----------+--------------+----------------------------------+
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| flag bit | cpuid bit | meaning |
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+-----------+--------------+----------------------------------+
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| | | time measures taken across |
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| 0 | 24 | multiple cpus are guaranteed to |
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| | | be monotonic |
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+-----------+--------------+----------------------------------+
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| | | guest vcpu has been paused by |
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| 1 | N/A | the host |
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| | | See 4.70 in api.txt |
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+-----------+--------------+----------------------------------+
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Availability of this MSR must be checked via bit 3 in 0x4000001 cpuid
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leaf prior to usage.
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MSR_KVM_WALL_CLOCK: 0x11
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MSR_KVM_WALL_CLOCK:
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0x11
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data and functioning: same as MSR_KVM_WALL_CLOCK_NEW. Use that instead.
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data and functioning:
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same as MSR_KVM_WALL_CLOCK_NEW. Use that instead.
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This MSR falls outside the reserved KVM range and may be removed in the
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future. Its usage is deprecated.
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@ -136,9 +157,11 @@ MSR_KVM_WALL_CLOCK: 0x11
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Availability of this MSR must be checked via bit 0 in 0x4000001 cpuid
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leaf prior to usage.
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MSR_KVM_SYSTEM_TIME: 0x12
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MSR_KVM_SYSTEM_TIME:
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0x12
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data and functioning: same as MSR_KVM_SYSTEM_TIME_NEW. Use that instead.
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data and functioning:
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same as MSR_KVM_SYSTEM_TIME_NEW. Use that instead.
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This MSR falls outside the reserved KVM range and may be removed in the
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future. Its usage is deprecated.
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@ -146,7 +169,7 @@ MSR_KVM_SYSTEM_TIME: 0x12
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Availability of this MSR must be checked via bit 0 in 0x4000001 cpuid
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leaf prior to usage.
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The suggested algorithm for detecting kvmclock presence is then:
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The suggested algorithm for detecting kvmclock presence is then::
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if (!kvm_para_available()) /* refer to cpuid.txt */
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return NON_PRESENT;
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@ -163,8 +186,11 @@ MSR_KVM_SYSTEM_TIME: 0x12
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} else
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return NON_PRESENT;
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MSR_KVM_ASYNC_PF_EN: 0x4b564d02
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data: Bits 63-6 hold 64-byte aligned physical address of a
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MSR_KVM_ASYNC_PF_EN:
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0x4b564d02
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data:
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Bits 63-6 hold 64-byte aligned physical address of a
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64 byte memory area which must be in guest RAM and must be
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zeroed. Bits 5-3 are reserved and should be zero. Bit 0 is 1
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when asynchronous page faults are enabled on the vcpu 0 when
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@ -200,20 +226,22 @@ MSR_KVM_ASYNC_PF_EN: 0x4b564d02
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Currently type 2 APF will be always delivered on the same vcpu as
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type 1 was, but guest should not rely on that.
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MSR_KVM_STEAL_TIME: 0x4b564d03
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MSR_KVM_STEAL_TIME:
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0x4b564d03
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data: 64-byte alignment physical address of a memory area which must be
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data:
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64-byte alignment physical address of a memory area which must be
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in guest RAM, plus an enable bit in bit 0. This memory is expected to
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hold a copy of the following structure:
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hold a copy of the following structure::
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struct kvm_steal_time {
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struct kvm_steal_time {
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__u64 steal;
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__u32 version;
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__u32 flags;
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__u8 preempted;
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__u8 u8_pad[3];
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__u32 pad[11];
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}
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}
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whose data will be filled in by the hypervisor periodically. Only one
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write, or registration, is needed for each VCPU. The interval between
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@ -224,25 +252,32 @@ MSR_KVM_STEAL_TIME: 0x4b564d03
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Fields have the following meanings:
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version: a sequence counter. In other words, guest has to check
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version:
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a sequence counter. In other words, guest has to check
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this field before and after grabbing time information and make
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sure they are both equal and even. An odd version indicates an
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in-progress update.
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flags: At this point, always zero. May be used to indicate
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flags:
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At this point, always zero. May be used to indicate
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changes in this structure in the future.
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steal: the amount of time in which this vCPU did not run, in
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steal:
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the amount of time in which this vCPU did not run, in
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nanoseconds. Time during which the vcpu is idle, will not be
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reported as steal time.
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preempted: indicate the vCPU who owns this struct is running or
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preempted:
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indicate the vCPU who owns this struct is running or
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not. Non-zero values mean the vCPU has been preempted. Zero
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means the vCPU is not preempted. NOTE, it is always zero if the
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the hypervisor doesn't support this field.
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MSR_KVM_EOI_EN: 0x4b564d04
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data: Bit 0 is 1 when PV end of interrupt is enabled on the vcpu; 0
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MSR_KVM_EOI_EN:
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0x4b564d04
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data:
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Bit 0 is 1 when PV end of interrupt is enabled on the vcpu; 0
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when disabled. Bit 1 is reserved and must be zero. When PV end of
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interrupt is enabled (bit 0 set), bits 63-2 hold a 4-byte aligned
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physical address of a 4 byte memory area which must be in guest RAM and
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@ -274,11 +309,13 @@ MSR_KVM_EOI_EN: 0x4b564d04
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clear it using a single CPU instruction, such as test and clear, or
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compare and exchange.
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MSR_KVM_POLL_CONTROL: 0x4b564d05
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MSR_KVM_POLL_CONTROL:
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0x4b564d05
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Control host-side polling.
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data: Bit 0 enables (1) or disables (0) host-side HLT polling logic.
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data:
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Bit 0 enables (1) or disables (0) host-side HLT polling logic.
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KVM guests can request the host not to poll on HLT, for example if
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they are performing polling themselves.
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