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| author | Glauber Costa <glommer@redhat.com> | 2010-05-11 18:17:47 +0200 |
|---|---|---|
| committer | Avi Kivity <avi@redhat.com> | 2010-05-19 10:41:07 +0200 |
| commit | 09c9e81366b9167b88ff05cf29fa94dc3553eb3d (patch) | |
| tree | b2555594894cbd5768ee01331fb3a3a7686e6481 /Documentation/kvm | |
| parent | KVM: x86: Tell the guest we'll warn it about tsc stability (diff) | |
| download | linux-09c9e81366b9167b88ff05cf29fa94dc3553eb3d.tar.xz linux-09c9e81366b9167b88ff05cf29fa94dc3553eb3d.zip | |
KVM: Add cpuid.txt file
This file documents cpuid bits used by KVM.
Signed-off-by: Glauber Costa <glommer@redhat.com>
Acked-by: Zachary Amsden <zamsden@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Diffstat (limited to 'Documentation/kvm')
| -rw-r--r-- | Documentation/kvm/cpuid.txt | 42 |
1 files changed, 42 insertions, 0 deletions
diff --git a/Documentation/kvm/cpuid.txt b/Documentation/kvm/cpuid.txt new file mode 100644 index 000000000000..14a12ea92b7f --- /dev/null +++ b/Documentation/kvm/cpuid.txt @@ -0,0 +1,42 @@ +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 = 0, + ebx = 0x4b4d564b, + ecx = 0x564b4d56, + edx = 0x4d. +Note that this value in ebx, ecx and edx corresponds to the string "KVMKVMKVM". +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_CLOCKSOURCE_STABLE_BIT || 24 || host will warn if no guest-side + || || per-cpu warps are expected in + || || kvmclock. +------------------------------------------------------------------------------ |