linux-kernel - Re: [PATCH v2] KVM: SVM: emulate MSR_IA32_PERF

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Message-ID: <adc8b307-4ec4-575f-ff94-c9b820189fb1@redhat.com>
Date:   Thu, 18 Jun 2020 14:10:44 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>, kvm@...r.kernel.org
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Like Xu <like.xu@...ux.intel.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] KVM: SVM: emulate MSR_IA32_PERF_CAPABILITIES

On 18/06/20 13:13, Vitaly Kuznetsov wrote:
> state_test/smm_test selftests are failing on AMD with:
> "Unexpected result from KVM_GET_MSRS, r: 51 (failed MSR was 0x345)"
> 
> MSR_IA32_PERF_CAPABILITIES is an emulated MSR on Intel but it is not
> known to AMD code, emulate it there too (by returning 0 and allowing
> userspace to write 0). This way the code is better prepared to the
> eventual appearance of the feature in AMD hardware.
> 
> Fixes: 27461da31089 ("KVM: x86/pmu: Support full width counting")
> Suggested-by: Jim Mattson <jmattson@...gle.com>
> Suggested-by: Paolo Bonzini <pbonzini@...hat.com>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
> ---
>  arch/x86/kvm/svm/pmu.c | 29 ++++++++++++++++++++++++++++-
>  1 file changed, 28 insertions(+), 1 deletion(-)

This is okay and I'll apply it, but it would be even better to move the
whole handling of the MSR to common x86 code.

Paolo