linux-kernel - Re: [PATCH v2 2/3] KVM: x86/svm/pmu: Add AMD PerfMonV2 support

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Date:   Tue, 20 Sep 2022 17:06:47 -0700
From:   Jim Mattson <jmattson@...gle.com>
To:     Like Xu <like.xu.linux@...il.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Sandipan Das <sandipan.das@....com>
Subject: Re: [PATCH v2 2/3] KVM: x86/svm/pmu: Add AMD PerfMonV2 support

On Mon, Sep 19, 2022 at 2:35 AM Like Xu <like.xu.linux@...il.com> wrote:
>
> From: Like Xu <likexu@...cent.com>
>
> If AMD Performance Monitoring Version 2 (PerfMonV2) is detected
> by the guest, it can use a new scheme to manage the Core PMCs using
> the new global control and status registers.
>
> In addition to benefiting from the PerfMonV2 functionality in the same
> way as the host (higher precision), the guest also can reduce the number
> of vm-exits by lowering the total number of MSRs accesses.
>
> In terms of implementation details, amd_is_valid_msr() is resurrected
> since three newly added MSRs could not be mapped to one vPMC.
> The possibility of emulating PerfMonV2 on the mainframe has also
> been eliminated for reasons of precision.
>
> Co-developed-by: Sandipan Das <sandipan.das@....com>
> Signed-off-by: Sandipan Das <sandipan.das@....com>
> Signed-off-by: Like Xu <likexu@...cent.com>
Reviewed-by: Jim Mattson <jmattson@...gle.com>