linux-kernel - Re: [PATCH v2 22/28] KVM: VMX: Clear controls obsoleted by EPT at runtime, not setup

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Message-ID: <Ysc0TZaKxweEaelb@google.com>
Date:   Thu, 7 Jul 2022 19:30:21 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     Jim Mattson <jmattson@...gle.com>, kvm@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Anirudh Rayabharam <anrayabh@...ux.microsoft.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 22/28] KVM: VMX: Clear controls obsoleted by EPT at
 runtime, not setup

On Thu, Jul 07, 2022, Vitaly Kuznetsov wrote:
> Jim Mattson <jmattson@...gle.com> writes:
> 
> > On Wed, Jun 29, 2022 at 8:07 AM Vitaly Kuznetsov <vkuznets@...hat.com> wrote:
> >>
> >> From: Sean Christopherson <seanjc@...gle.com>
> >>
> >> Clear the CR3 and INVLPG interception controls at runtime based on
> >> whether or not EPT is being _used_, as opposed to clearing the bits at
> >> setup if EPT is _supported_ in hardware, and then restoring them when EPT
> >> is not used.  Not mucking with the base config will allow using the base
> >> config as the starting point for emulating the VMX capability MSRs.
> >>
> >> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> >> Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
> > Nit: These controls aren't "obsoleted" by EPT; they're just no longer
> > required.

Isn't that the definition of "obsolete"?  They're "no longer in use" when KVM
enables EPT.

> I'm going to update the subject line to "KVM: VMX: Clear controls
> unneded with EPT at runtime, not setup" retaining your authorship in v3

That's fine, though s/unneded/unneeded.