linux-kernel - Re: [PATCH 42/43] KVM: VMX: Drop VMWRITEs to zero fields at vCPU RESET

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Message-ID: <CALMp9eT72keN2r9tfdzsPpzAkV9fN4V4edmXuPyMbt+shVu0Ww@mail.gmail.com>
Date:   Mon, 24 May 2021 15:21:20 -0700
From:   Jim Mattson <jmattson@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Joerg Roedel <joro@...tes.org>, kvm list <kvm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 42/43] KVM: VMX: Drop VMWRITEs to zero fields at vCPU RESET

On Mon, May 24, 2021 at 2:15 PM Paolo Bonzini <pbonzini@...hat.com> wrote:
>
> On 24/04/21 02:46, Sean Christopherson wrote:
> > Don't waste time writing zeros via VMWRITE during vCPU RESET, the VMCS
> > is zero allocated.
>
> Is this guaranteed to be valid, or could the VMCS in principle use some
> weird encoding? (Like it does for the access rights, even though this
> does not matter for this patch).

I see nothing in the SDM that would indicate that zero must be encoded as zero.