On 09/01/2018 12:14, David Hildenbrand wrote: >> >> +/* These are scattered features in cpufeatures.h. */ >> +#define KVM_CPUID_BIT_AVX512_4VNNIW 2 >> +#define KVM_CPUID_BIT_AVX512_4FMAPS 3 >> +#define KVM_CPUID_BIT_SPEC_CTRL 26 >> +#define KVM_CPUID_BIT_STIBP 27 > I can see that STIBP is never checked in KVM code but only forwarded to > the guest if available. > > I am wondering if we would have to check against that, too, before > issuing a FEATURE_SET_IBPB. STIBP is "single-threaded indirect branch prediction". SPEC_CTRL always implies that FEATURE_SET_IBPB is available. Paolo
