linux-kernel - Re: [PATCH 1/3] KVM: x86: use native MSR ops for SPEC

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Message-ID: <CALMp9eQX6DQ8qUZ2+Ri4V6cxaFx-C-ysz9sq=j6LXzs+prNciQ@mail.gmail.com>
Date:   Wed, 21 Feb 2018 15:49:59 -0800
From:   Jim Mattson <jmattson@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        kvm list <kvm@...r.kernel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Radim Krčmář <rkrcmar@...hat.com>,
        KarimAllah Ahmed <karahmed@...zon.de>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>, stable@...r.kernel.org
Subject: Re: [PATCH 1/3] KVM: x86: use native MSR ops for SPEC_CTRL

On Wed, Feb 21, 2018 at 1:41 PM, Paolo Bonzini <pbonzini@...hat.com> wrote:
> Having a paravirt indirect call in the IBRS restore path is not a
> good idea, since we are trying to protect from speculative execution
> of bogus indirect branch targets.  It is also slower, so use
> native_wrmsrl on the vmentry path too.
>
> Fixes: d28b387fb74da95d69d2615732f50cceb38e9a4d
> Cc: x86@...nel.org
> Cc: Radim Krčmář <rkrcmar@...hat.com>
> Cc: KarimAllah Ahmed <karahmed@...zon.de>
> Cc: David Woodhouse <dwmw@...zon.co.uk>
> Cc: Jim Mattson <jmattson@...gle.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...nel.org>
> Cc: stable@...r.kernel.org
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>

Seems like there ought to be a native_rdmsrl, but otherwise this looks fine.

Reviewed-by: Jim Mattson <jmattson@...gle.com>