linux-kernel - Re: [PATCH v4] KVM: emulate: Don't inject #GP when emulating RDMPC if CR0.PE=0

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Date:   Wed, 20 Oct 2021 11:01:58 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Wanpeng Li <kernellwp@...il.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     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 v4] KVM: emulate: Don't inject #GP when emulating RDMPC if
 CR0.PE=0

On 20/10/21 10:52, Wanpeng Li wrote:
> From: Wanpeng Li<wanpengli@...cent.com>
> 
> SDM mentioned that we should #GP for rdpmc if ECX is not valid or
> (CR4.PCE is 0 and CPL is 1, 2, or 3 and CR0.PE is 1).
> 
> 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.
> 
> Reviewed-by: Sean Christopherson<seanjc@...gle.com>
> Signed-off-by: Wanpeng Li<wanpengli@...cent.com>
> ---
> v3 -> v4:
>   * add comments instead of pseudocode

No, the commit message was fine.  What I meant is there's no need to 
change the code.  Just add a comment about why CR0.PE isn't tested.

Paolo