Re: [PATCH] KVM: CPUID: Add new features to the guest's CPUID

[Aaron Lewis <aaronlewis@google.com>]

On Mon, Jul 15, 2019 at 2:03 PM Aaron Lewis <aaronlewis@google.com> wrote:
>
> Add features X86_FEATURE_FDP_EXCPTN_ONLY and X86_FEATURE_ZERO_FCS_FDS to the
> mask for CPUID.(EAX=07H,ECX=0H):EBX.  Doing this will ensure the guest's CPUID
> for these bits match the host, rather than the guest being blindly set to 0.
>
> This is important as these are actually defeature bits, which means that
> a 0 indicates the presence of a feature and a 1 indicates the absence of
> a feature.  since these features cannot be emulated, kvm should not
> claim the existence of a feature that isn't present on the host.
>
> Signed-off-by: Aaron Lewis <aaronlewis@google.com>
> ---
>  arch/x86/kvm/cpuid.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index ead681210306..64c3fad068e1 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -353,7 +353,8 @@ static inline void do_cpuid_7_mask(struct kvm_cpuid_entry2 *entry, int index)
>                 F(BMI2) | F(ERMS) | f_invpcid | F(RTM) | f_mpx | F(RDSEED) |
>                 F(ADX) | F(SMAP) | F(AVX512IFMA) | F(AVX512F) | F(AVX512PF) |
>                 F(AVX512ER) | F(AVX512CD) | F(CLFLUSHOPT) | F(CLWB) | F(AVX512DQ) |
> -               F(SHA_NI) | F(AVX512BW) | F(AVX512VL) | f_intel_pt;
> +               F(SHA_NI) | F(AVX512BW) | F(AVX512VL) | f_intel_pt |
> +               F(FDP_EXCPTN_ONLY) | F(ZERO_FCS_FDS);
>
>         /* cpuid 7.0.ecx*/
>         const u32 kvm_cpuid_7_0_ecx_x86_features =
> --
> 2.22.0.510.g264f2c817a-goog
>

ping