diff options
author | Glauber Costa <glommer@redhat.com> | 2010-05-11 12:17:47 -0400 |
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committer | Avi Kivity <avi@redhat.com> | 2010-05-19 04:41:07 -0400 |
commit | 09c9e81366b9167b88ff05cf29fa94dc3553eb3d (patch) | |
tree | b2555594894cbd5768ee01331fb3a3a7686e6481 /Documentation | |
parent | 371bcf646d170ee1325abaf4f3e73485b4fd4d2d (diff) |
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')
-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 @@ | |||
1 | KVM CPUID bits | ||
2 | Glauber Costa <glommer@redhat.com>, Red Hat Inc, 2010 | ||
3 | ===================================================== | ||
4 | |||
5 | A guest running on a kvm host, can check some of its features using | ||
6 | cpuid. This is not always guaranteed to work, since userspace can | ||
7 | mask-out some, or even all KVM-related cpuid features before launching | ||
8 | a guest. | ||
9 | |||
10 | KVM cpuid functions are: | ||
11 | |||
12 | function: KVM_CPUID_SIGNATURE (0x40000000) | ||
13 | returns : eax = 0, | ||
14 | ebx = 0x4b4d564b, | ||
15 | ecx = 0x564b4d56, | ||
16 | edx = 0x4d. | ||
17 | Note that this value in ebx, ecx and edx corresponds to the string "KVMKVMKVM". | ||
18 | This function queries the presence of KVM cpuid leafs. | ||
19 | |||
20 | |||
21 | function: define KVM_CPUID_FEATURES (0x40000001) | ||
22 | returns : ebx, ecx, edx = 0 | ||
23 | eax = and OR'ed group of (1 << flag), where each flags is: | ||
24 | |||
25 | |||
26 | flag || value || meaning | ||
27 | ============================================================================= | ||
28 | KVM_FEATURE_CLOCKSOURCE || 0 || kvmclock available at msrs | ||
29 | || || 0x11 and 0x12. | ||
30 | ------------------------------------------------------------------------------ | ||
31 | KVM_FEATURE_NOP_IO_DELAY || 1 || not necessary to perform delays | ||
32 | || || on PIO operations. | ||
33 | ------------------------------------------------------------------------------ | ||
34 | KVM_FEATURE_MMU_OP || 2 || deprecated. | ||
35 | ------------------------------------------------------------------------------ | ||
36 | KVM_FEATURE_CLOCKSOURCE2 || 3 || kvmclock available at msrs | ||
37 | || || 0x4b564d00 and 0x4b564d01 | ||
38 | ------------------------------------------------------------------------------ | ||
39 | KVM_FEATURE_CLOCKSOURCE_STABLE_BIT || 24 || host will warn if no guest-side | ||
40 | || || per-cpu warps are expected in | ||
41 | || || kvmclock. | ||
42 | ------------------------------------------------------------------------------ | ||