linux-kernel - Re: [PATCH RFC 1/5] x86: KVM: svm: don't pretend to advance RIP in case wrmsr

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Message-ID: <CALMp9eTZSWA-7SOHS=2xrMKaXv_imKpURHGcDpfgusF+JDXFMg@mail.gmail.com>
Date:   Thu, 20 Jun 2019 11:49:11 -0700
From:   Jim Mattson <jmattson@...gle.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     kvm list <kvm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Joerg Roedel <joro@...tes.org>
Subject: Re: [PATCH RFC 1/5] x86: KVM: svm: don't pretend to advance RIP in
 case wrmsr_interception() results in #GP

On Thu, Jun 20, 2019 at 4:02 AM Vitaly Kuznetsov <vkuznets@...hat.com> wrote:
>
> svm->next_rip is only used by skip_emulated_instruction() and in case
> kvm_set_msr() fails we rightfully don't do that. Move svm->next_rip
> advancement to 'else' branch to avoid creating false impression that
> it's always advanced.
>
> By the way, rdmsr_interception() has it right already.

I think I actually prefer the current placement, because this allows
the code that's common to both kvm-amd.ko and kvm-intel.ko to be
hoisted into the vendor-agnostic kvm module. Also, this hard-coded '2'
should be going away, right?