linux-kernel - Re: [PATCH v2 0/2] INVD intercept change to skip instruction

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Message-ID: <CALMp9eS2C398GUKm9FP6xdVLN=NYTO3y+EMKv0ptGJ_dzxkP+g@mail.gmail.com>
Date:   Thu, 24 Sep 2020 14:20:33 -0700
From:   Jim Mattson <jmattson@...gle.com>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     kvm list <kvm@...r.kernel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Joerg Roedel <joro@...tes.org>,
        Brijesh Singh <brijesh.singh@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v2 0/2] INVD intercept change to skip instruction

On Thu, Sep 24, 2020 at 11:42 AM Tom Lendacky <thomas.lendacky@....com> wrote:
>
> From: Tom Lendacky <thomas.lendacky@....com>
>
> This series updates the INVD intercept support for both SVM and VMX to
> skip the instruction rather than emulating it, since emulation of this
> instruction is just a NOP.

Isn't INVD a serializing instruction, whereas NOP isn't? IIRC, Intel
doesn't architect VM-entry or VM-exit as serializing, though they
probably are in practice. I'm not sure what AMD's stance on this is.