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From: Aaron Lewis <aaronlewis@google.com>
To: Krish Sadhukhan <krish.sadhukhan@oracle.com>
Cc: Jim Mattson <jmattson@google.com>, kvm@vger.kernel.org
Subject: Re: [PATCH] KVM: CPUID: Add new features to the guest's CPUID
Date: Wed, 21 Aug 2019 09:17:57 -0700
Message-ID: <CAAAPnDE_m0YEd6tjRVsEppP_kD5itfN2q2EBRVAvjyNPEm_+gQ@mail.gmail.com> (raw)
In-Reply-To: <87d3c508-31be-1264-e168-c72b6857d000@oracle.com>

On Tue, Jul 23, 2019 at 2:42 PM Krish Sadhukhan
<krish.sadhukhan@oracle.com> wrote:
>
>
>
> On 07/15/2019 02:03 PM, Aaron Lewis 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>
> > Reviewed-by: Krish Sadhukhan <krish.sadhukhan@oracle.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 =
>
> Reviewed-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>

ping

      reply index

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-15 21:03 Aaron Lewis
2019-07-22 14:51 ` Aaron Lewis
2019-07-23 21:42 ` Krish Sadhukhan
2019-08-21 16:17   ` Aaron Lewis [this message]

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