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Subject: Re: [RESEND v13 00/10] KVM: x86/pmu: Guest Last Branch Recording
 Enabling
To:     Like Xu <like.xu@linux.intel.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Sean Christopherson <seanjc@google.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>
Cc:     Ingo Molnar <mingo@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Borislav Petkov <bp@alien8.de>,
        "H . Peter Anvin" <hpa@zytor.com>, ak@linux.intel.com,
        wei.w.wang@intel.com, kan.liang@intel.com, x86@kernel.org,
        kvm@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20210108013704.134985-1-like.xu@linux.intel.com>
From:   Alex Shi <alex.shi@linux.alibaba.com>
Message-ID: <3deac361-05fa-60a5-0d88-4f6b968f10bf@linux.alibaba.com>
Date:   Fri, 15 Jan 2021 16:19:06 +0800
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?? 2021/1/8 ????9:36, Like Xu д??:
> Because saving/restoring tens of LBR MSRs (e.g. 32 LBR stack entries) in
> VMX transition brings too excessive overhead to frequent vmx transition
> itself, the guest LBR event would help save/restore the LBR stack msrs
> during the context switching with the help of native LBR event callstack
> mechanism, including LBR_SELECT msr.
> 

Sounds the feature is much helpful for VMM guest performance tunning.
Good job!

Thanks
Alex