linux-kernel - Re: [PATCH v2 0/2] KVM: x86: expose direct stores instructions into VM.

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Message-ID: <CAG7+5M0XNw6KOTw6JyqT67fp3cAX=MseT1A0_1Zpb6UM_O3fLw@mail.gmail.com>
Date:   Fri, 30 Nov 2018 12:41:44 -0800
From:   Eric Northup <digitaleric@...gle.com>
To:     jingqi.liu@...el.com
Cc:     Paolo Bonzini <pbonzini@...hat.com>, rkrcmar@...hat.com,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, bp@...en8.de,
        "H. Peter Anvin" <hpa@...or.com>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        KVM <kvm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        tao3.xu@...el.com
Subject: Re: [PATCH v2 0/2] KVM: x86: expose direct stores instructions into VM.

On Mon, Nov 5, 2018 at 10:01 PM Liu Jingqi <jingqi.liu@...el.com> wrote:
>
> Direct stores instructions MOVDIRI and MOVDIR64B will be available in
> Tremont and other future x86 processors,
> and need to be exposed to guest VM.

It seems like KVM's emulator should be able to complete these
instructions to emulated MMIO before exposing CPUID to guests in any
default or supported configurations.

It'll be much simpler for usermode to implement that property if the
KVM-reported supported CPUID table doesn't get updated before the KVM
emulator does.

-Eric