Based on kernel version 2.6.39.1. Page generated on 2011-06-03 13:47 EST.
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 ------------------------------------------------------------------------------