linux-kernel - Re: [PATCH v3 1/3] KVM: emulate: Don't inject #GP when emulating RDMPC if CR0.PE=0

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Message-ID: <CANRm+CxXogoP0vh9_qPz_d4+p+ZQwy_SdJ6exuG1dd7+3weHSg@mail.gmail.com>
Date:   Wed, 20 Oct 2021 09:56:03 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>
Subject: Re: [PATCH v3 1/3] KVM: emulate: Don't inject #GP when emulating
 RDMPC if CR0.PE=0

On Wed, 20 Oct 2021 at 01:00, Paolo Bonzini <pbonzini@...hat.com> wrote:
>
> On 19/10/21 10:12, Wanpeng Li wrote:
> > From: Wanpeng Li <wanpengli@...cent.com>
> >
> > SDM mentioned that, RDPMC:
> >
> >    IF (((CR4.PCE = 1) or (CPL = 0) or (CR0.PE = 0)) and (ECX indicates a supported counter))
> >        THEN
> >            EAX := counter[31:0];
> >            EDX := ZeroExtend(counter[MSCB:32]);
> >        ELSE (* ECX is not valid or CR4.PCE is 0 and CPL is 1, 2, or 3 and CR0.PE is 1 *)
> >            #GP(0);
> >    FI;
> >
> > Let's add the CR0.PE is 1 checking to rdpmc emulate, though this isn't
> > strictly necessary since it's impossible for CPL to be >0 if CR0.PE=0.
>
> Why not just add a comment then instead?

Will do.

    Wanpeng