| 123456789101112131415161718192021222324252627282930313233343536373839404142434445 |
- 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_ASYNC_PF || 4 || async pf can be enabled by
- || || writing to msr 0x4b564d02
- ------------------------------------------------------------------------------
- KVM_FEATURE_CLOCKSOURCE_STABLE_BIT || 24 || host will warn if no guest-side
- || || per-cpu warps are expected in
- || || kvmclock.
- ------------------------------------------------------------------------------
|
