linux-kernel - Re: [PATCH v3 5/7] KVM: x86/pmu: Defer counter emulated overflow via pmc->prev

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Message-ID: <341cffc3-d0b9-2ef7-3c6e-c48ea179699b@gmail.com>
Date:   Fri, 14 Oct 2022 16:08:20 +0800
From:   Like Xu <like.xu.linux@...il.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 5/7] KVM: x86/pmu: Defer counter emulated overflow via
 pmc->prev_counter

On 23/9/2022 7:59 am, Sean Christopherson wrote:
> The bigger issue is that calling __kvm_perf_overflow() here can get false negatives.
> If reprogramming fails due to contention, the reprogram_pmi bit will be left set
> and so this check in __kvm_perf_overflow() will suppress the PMI.

I understand your motivation, and before we reprocess on "left set reprogram_pmi 
bit",
we may need reproducible cases to cover "reprogramming fails".