Re: [PATCH] EDAC/mce_amd: Reduce unnecessary spew in dmesg if SMCA feature bit is not exposed

[Borislav Petkov]

On Tue, Jun 15, 2021 at 12:32:21PM -0400, Yazen Ghannam wrote:
> Yes, I agree. I was a bit confused about the X86_FEATURE_HYPERVISOR
> thing, but I think I get it. This definitely looks simple to do.

Yeah, if you look at the qemu repo:

kvm_arch_get_supported_cpuid:

...

    } else if (function == 1 && reg == R_ECX) {
        /* We can set the hypervisor flag, even if KVM does not return it on
         * GET_SUPPORTED_CPUID
         */
        ret |= CPUID_EXT_HYPERVISOR;


so long story short, that thing is set by the HV and there's an
"agreement" of sorts and APM v3 even says so:

"CPUID Fn0000_0001_ECX Feature Identifiers

...

31:	RAZ. Reserved for use by hypervisor to indicate guest status."

HTH.

-- 
Regards/Gruss,
    Boris.

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