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| author | Michael J. Chudobiak <mjc@avtechpulse.com> | 2016-04-25 10:00:44 -0400 |
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| committer | Michael J. Chudobiak <mjc@avtechpulse.com> | 2016-04-25 10:00:44 -0400 |
| commit | a1df417e74aa6dae7352dc8cbb0ad471af5b7c69 (patch) | |
| tree | c34b2311e37ea31db153c90cb8f4570374d05e78 /linux/Documentation/virtual/kvm/cpuid.txt | |
initial Olimex linux tree from Daniel, originally Feb 3, 2016
Diffstat (limited to 'linux/Documentation/virtual/kvm/cpuid.txt')
| -rw-r--r-- | linux/Documentation/virtual/kvm/cpuid.txt | 60 |
1 files changed, 60 insertions, 0 deletions
diff --git a/linux/Documentation/virtual/kvm/cpuid.txt b/linux/Documentation/virtual/kvm/cpuid.txt new file mode 100644 index 00000000..3c65feb8 --- /dev/null +++ b/linux/Documentation/virtual/kvm/cpuid.txt @@ -0,0 +1,60 @@ +KVM CPUID bits +Glauber Costa <glommer@redhat.com>, Red Hat Inc, 2010 +===================================================== + +A guest running on a kvm host, can check some of its features using +cpuid. This is not always guaranteed to work, since userspace can +mask-out some, or even all KVM-related cpuid features before launching +a guest. + +KVM cpuid functions are: + +function: KVM_CPUID_SIGNATURE (0x40000000) +returns : eax = 0x40000001, + ebx = 0x4b4d564b, + ecx = 0x564b4d56, + edx = 0x4d. +Note that this value in ebx, ecx and edx corresponds to the string "KVMKVMKVM". +The value in eax corresponds to the maximum cpuid function present in this leaf, +and will be updated if more functions are added in the future. +Note also that old hosts set eax value to 0x0. This should +be interpreted as if the value was 0x40000001. +This function queries the presence of KVM cpuid leafs. + + +function: define KVM_CPUID_FEATURES (0x40000001) +returns : ebx, ecx, edx = 0 + eax = and OR'ed group of (1 << flag), where each flags is: + + +flag || value || meaning +============================================================================= +KVM_FEATURE_CLOCKSOURCE || 0 || kvmclock available at msrs + || || 0x11 and 0x12. +------------------------------------------------------------------------------ +KVM_FEATURE_NOP_IO_DELAY || 1 || not necessary to perform delays + || || on PIO operations. +------------------------------------------------------------------------------ +KVM_FEATURE_MMU_OP || 2 || deprecated. +------------------------------------------------------------------------------ +KVM_FEATURE_CLOCKSOURCE2 || 3 || kvmclock available at msrs + || || 0x4b564d00 and 0x4b564d01 +------------------------------------------------------------------------------ +KVM_FEATURE_ASYNC_PF || 4 || async pf can be enabled by + || || writing to msr 0x4b564d02 +------------------------------------------------------------------------------ +KVM_FEATURE_STEAL_TIME || 5 || steal time can be enabled by + || || writing to msr 0x4b564d03. +------------------------------------------------------------------------------ +KVM_FEATURE_PV_EOI || 6 || paravirtualized end of interrupt + || || handler can be enabled by writing + || || to msr 0x4b564d04. +------------------------------------------------------------------------------ +KVM_FEATURE_PV_UNHALT || 7 || guest checks this feature bit + || || before enabling paravirtualized + || || spinlock support. +------------------------------------------------------------------------------ +KVM_FEATURE_CLOCKSOURCE_STABLE_BIT || 24 || host will warn if no guest-side + || || per-cpu warps are expected in + || || kvmclock. +------------------------------------------------------------------------------ |