linux-kernel - Re: [PATCH v2 07/21] KVM: x86/pmu: Zero out LBR capabilities during PMU refresh

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Date:   Wed, 15 Feb 2023 07:17:13 -0800
From:   Sean Christopherson <seanjc@...gle.com>
To:     Like Xu <like.xu.linux@...il.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH v2 07/21] KVM: x86/pmu: Zero out LBR capabilities during
 PMU refresh

On Wed, Feb 15, 2023, Like Xu wrote:
> On 10/2/2023 8:31 am, Sean Christopherson wrote:
> > Note, this is a very theoretical bug, there is no known use case where a
> > VMM would deliberately enable the vPMU via KVM_SET_CPUID2, and then later
> > disable the vPMU.
> 
> That's why we're getting more and more comfortable with selftests
> and fuzz testing on KVM interfaces. So is there a test for this ?

Yep, last patch in the series, "KVM: selftests: Verify LBRs are disabled if vPMU
is disabled".