linux-kernel - Re: [RESEND v13 00/10] KVM: x86/pmu: Guest Last Branch Recording Enabling

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Date:   Fri, 15 Jan 2021 16:51:01 +0800
From:   "Xu, Like" <like.xu@...el.com>
To:     Alex Shi <alex.shi@...ux.alibaba.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>, ak@...ux.intel.com,
        wei.w.wang@...el.com, kan.liang@...el.com, x86@...nel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Joerg Roedel <joro@...tes.org>,
        Jim Mattson <jmattson@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Like Xu <like.xu@...ux.intel.com>
Subject: Re: [RESEND v13 00/10] KVM: x86/pmu: Guest Last Branch Recording
 Enabling

Hi Alex,

Thank you for trying this guest feature on multiple Intel platforms!
If you have more specific comments or any concerns, just let me know.

---
thx, likexu

On 2021/1/15 16:19, Alex Shi wrote:
>
> 在 2021/1/8 上午9:36, Like Xu 写道:
>> 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