linux-kernel - Re: [PATCH v2 1/3] KVM: x86/pmu: Make part of the Intel v2 PMU MSRs handling x86 generic

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Message-ID: <Y1sCtGvXKi3wY0vp@google.com>
Date:   Thu, 27 Oct 2022 22:14:12 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Like Xu <like.xu.linux@...il.com>
Cc:     Jim Mattson <jmattson@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/3] KVM: x86/pmu: Make part of the Intel v2 PMU MSRs
 handling x86 generic

On Thu, Sep 22, 2022, Like Xu wrote:
> Subject: [PATCH] KVM: x86/pmu: Rewrite reprogram_counters() to improve
>  performance
> 
> Before using pmu->reprogram_pmi, the test for a valid pmc is always
> applied. This part of the redundancy could be removed by setting the
> counters' bitmask directly, and furthermore triggering KVM_REQ_PMU
> only once to save more cycles.

Assuming you plan on posting this, please explicitly state what the patch does.
"This part of the redundancy could" only says what _could_ be done, not what is
actually done.  Oftentimes, a changelog will say something "could" be done when
talking about alternative solutions.  So when I see "could", I think "this is
what the patch _isn't_ doing".