← Back to branch summary

~ubuntu-branches/ubuntu/precise/linux-ti-omap4/precise

« back to all changes in this revision

Viewing changes to Documentation/virtual/kvm/cpuid.txt

  • Committer: Bazaar Package Importer
  • Author(s): Paolo Pisati
  • Date: 2011-06-29 15:23:51 UTC
  • mfrom: (26.1.1 natty-proposed)
  • Revision ID: james.westby@ubuntu.com-20110629152351-xs96tm303d95rpbk
Tags: 3.0.0-1200.2
* Rebased against 3.0.0-6.7
* BSP from TI based on 3.0.0

Show diffs side-by-side

added added

removed removed

Lines of Context:
Documentation/virtual/kvm/cpuid.txt
 
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_ASYNC_PF               ||     4 || async pf can be enabled by
 
40
                                   ||       || writing to msr 0x4b564d02
 
41
------------------------------------------------------------------------------
 
42
KVM_FEATURE_CLOCKSOURCE_STABLE_BIT ||    24 || host will warn if no guest-side
 
43
                                   ||       || per-cpu warps are expected in
 
44
                                   ||       || kvmclock.
 
45
------------------------------------------------------------------------------