linux-kernel - 答复: [PATCH] [RFC] kvm: x86: emulate APERF/MPERF registers

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Message-ID: <fd2a8092edf54a85979e5781dc354690@baidu.com>
Date:   Sun, 26 Apr 2020 03:24:13 +0000
From:   "Li,Rongqing" <lirongqing@...du.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>
CC:     Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        kvm list <kvm@...r.kernel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        "H . Peter Anvin" <hpa@...or.com>,
        "Borislav Petkov" <bp@...en8.de>, Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Joerg Roedel <joro@...tes.org>,
        Wanpeng Li <wanpengli@...cent.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>
Subject: 答复: [PATCH] [RFC] kvm: x86: emulate APERF/MPERF registers



> -----邮件原件-----
> 发件人: Paolo Bonzini [mailto:pbonzini@...hat.com]
> 发送时间: 2020年4月25日 0:30
> 收件人: Jim Mattson <jmattson@...gle.com>; Sean Christopherson
> <sean.j.christopherson@...el.com>
> 抄送: Peter Zijlstra <peterz@...radead.org>; Li,Rongqing
> <lirongqing@...du.com>; LKML <linux-kernel@...r.kernel.org>; kvm list
> <kvm@...r.kernel.org>; the arch/x86 maintainers <x86@...nel.org>; H .
> Peter Anvin <hpa@...or.com>; Borislav Petkov <bp@...en8.de>; Ingo Molnar
> <mingo@...hat.com>; Thomas Gleixner <tglx@...utronix.de>; Joerg Roedel
> <joro@...tes.org>; Wanpeng Li <wanpengli@...cent.com>; Vitaly Kuznetsov
> <vkuznets@...hat.com>
> 主题: Re: [PATCH] [RFC] kvm: x86: emulate APERF/MPERF registers
> 
> On 24/04/20 18:25, Jim Mattson wrote:
> >> Assuming we're going forward with this, at an absolute minimum the
> >> RDMSRs need to be wrapped with checks on host _and_ guest support for
> >> the emulated behavior.  Given the significant overhead, this might
> >> even be something that should require an extra opt-in from userspace to
> enable.
> >
> > I would like to see performance data before enabling this unconditionally.
> 
> I wouldn't want this to be enabled unconditionally anyway, because you need to
> take into account live migration to and from processors that do not have
> APERF/MPERF support.
> 
> Paolo

I will add a kvm parameter to consider whether enable MPERF/APERF emulations, and make default value to false

Thanks

-Li