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

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Message-ID: <87ftash6ui.fsf@vitty.brq.redhat.com>
Date:   Thu, 18 Jun 2020 14:54:45 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Paolo Bonzini <pbonzini@...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

Paolo Bonzini <pbonzini@...hat.com> writes:

> 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.

I thought about that but intel_pmu_set_msr() looks at
vmx_get_perf_capabilities(), we'll need to abstract this somehow.

-- 
Vitaly