linux-kernel - Re: [PATCH v2 2/3] kvm, vmx: move register clearing out of assembly path

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Date:   Thu, 1 Nov 2018 13:40:29 +0000
From:   "Stecklina, Julian" <jsteckli@...zon.de>
To:     "sean.j.christopherson@...el.com" <sean.j.christopherson@...el.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "js@...en8.de" <js@...en8.de>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>
Subject: Re: [PATCH v2 2/3] kvm, vmx: move register clearing out of assembly
 path

On Mon, 2018-10-29 at 10:26 -0700, Sean Christopherson wrote:
> I think it's a good idea to explicitly call out that clearing the
> GPRs
> is done to prevent speculative use.  Simply stating that we don't
> want
> to let guest register values survive doesn't explain *why*.
> 
> What about:
> 
>         /*
>          * Explicitly clear (in addition to marking them as
> clobbered) all GPRs
>          * that have not been loaded with host state to prevent
> speculatively
>          * using the guest's values.
>          */

Sounds good. I've also updated the commit message for the register
clearing commit. I'll repost the patches.

Julian



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