linux-kernel - RE: [PATCH v1 7/8] KVM: x86: Expose PEBS feature to guest

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Date:   Thu, 31 Oct 2019 04:21:08 +0000
From:   "Kang, Luwei" <luwei.kang@...el.com>
To:     Peter Zijlstra <peterz@...radead.org>
CC:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "rkrcmar@...hat.com" <rkrcmar@...hat.com>,
        "Christopherson, Sean J" <sean.j.christopherson@...el.com>,
        "vkuznets@...hat.com" <vkuznets@...hat.com>,
        "wanpengli@...cent.com" <wanpengli@...cent.com>,
        "jmattson@...gle.com" <jmattson@...gle.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
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        <alexander.shishkin@...ux.intel.com>,
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        "namhyung@...nel.org" <namhyung@...nel.org>
Subject: RE: [PATCH v1 7/8] KVM: x86: Expose PEBS feature to guest

> > > > Expose PEBS feature to guest by IA32_MISC_ENABLE[bit12].
> > > > IA32_MISC_ENABLE[bit12] is Processor Event Based Sampling (PEBS)
> > > > Unavailable (RO) flag:
> > > > 1 = PEBS is not supported; 0 = PEBS is supported.
> > >
> > > Why does it make sense to expose this on SVM?
> >
> > Thanks for the review. This patch won't expose the pebs feature to SVM and return not supported.
> 
> AFAICT it exposes/emulates an Intel MSR on AMD, which is just weird.

I checked with the "AMD64 Architecture Programmer's Manual" and didn't found this register (IA32_MISC_ENABLE).
Will move this register to vmx.c in next version.

Thanks,
Luwei Kang