On 01/08/2018 17:21, Brian Gerst wrote: > On Tue, Jul 31, 2018 at 9:00 AM Paolo Bonzini <pbonz...@redhat.com> wrote: >> >> On 31/07/2018 14:57, tedheadster wrote: >>>> >>>> This shouldn't be necessary; for systems that don't have virtualization >>>> extensions, the comment explains why setting X86_FEATURE_VMMCALL is safe. >>>> >>>> But it is also wrong, because you can run a 32-bit kernel as a guest on >>>> a 64-bit processor, and then it should set X86_FEATURE_VMMCALL because >>>> the processor has the vmmcall instruction and not Intel's vmcall. >>>> >>> >>> Paolo, >>> I'm running this on a bare metal machine (no virtualization) with a >>> 32-bit AMD i486 class cpu. Should the feature be showing up in >>> /proc/cpuinfo under the 'flags' line? It does on my machine, and it >>> looked wrong to me. >> >> It's a bit silly, but it's not particularly wrong. > > Why is there even a specific feature flag for VMMCALL? Isn't > X86_FEATURE_SVM sufficient to differentiate which opcode to use?
No, X86_FEATURE_SVM is there in the host while X86_FEATURE_VMMCALL is used in the guest. Paolo
