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References: <20231031090613.2872700-1-dapeng1.mi@linux.intel.com> <20231031090613.2872700-2-dapeng1.mi@linux.intel.com>
In-Reply-To: <20231031090613.2872700-2-dapeng1.mi@linux.intel.com>
From:   Jim Mattson <jmattson@google.com>
Date:   Tue, 31 Oct 2023 11:22:31 -0700
Message-ID: <CALMp9eR_BFdNNTXhSpbuH66jXcRLVB8VvD8V+kY245NbusN2+g@mail.gmail.com>
Subject: Re: [Patch 1/2] KVM: x86/pmu: Add Intel CPUID-hinted TopDown slots event
To:     Dapeng Mi <dapeng1.mi@linux.intel.com>
Cc:     Sean Christopherson <seanjc@google.com>,
        Paolo Bonzini <pbonzini@redhat.com>, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Zhenyu Wang <zhenyuw@linux.intel.com>,
        Zhang Xiong <xiong.y.zhang@intel.com>,
        Mingwei Zhang <mizhang@google.com>,
        Like Xu <like.xu.linux@gmail.com>,
        Dapeng Mi <dapeng1.mi@intel.com>, Like Xu <likexu@tencent.com>
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On Tue, Oct 31, 2023 at 1:58=E2=80=AFAM Dapeng Mi <dapeng1.mi@linux.intel.c=
om> wrote:
>
> This patch adds support for the architectural topdown slots event which
> is hinted by CPUID.0AH.EBX.

Can't a guest already program an event selector to count event select
0xa4, unit mask 1, unless the event is prohibited by
KVM_SET_PMU_EVENT_FILTER?

AFAICT, this change just enables event filtering based on
CPUID.0AH:EBX[bit 7] (though it's not clear to me why two independent
mechanisms are necessary for event filtering).