linux-kernel - Re: [PATCH v2 0/3] KVM: EFER.LMSLE cleanup

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Date:   Tue, 20 Sep 2022 21:36:18 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Jim Mattson <jmattson@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H . Peter Anvin" <hpa@...or.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH v2 0/3] KVM: EFER.LMSLE cleanup

On Tue, Sep 20, 2022, Borislav Petkov wrote:
> On Tue, Sep 20, 2022 at 01:59:19PM -0700, Jim Mattson wrote:
> > Jim Mattson (3):
> >   Revert "KVM: SVM: Allow EFER.LMSLE to be set with nested svm"
> >   x86/cpufeatures: Introduce X86_FEATURE_NO_LMSLE
> >   KVM: SVM: Unconditionally enumerate EferLmsleUnsupported
> 
> Why do you need those two if you revert the hack? After the revert,
> anything that tries to set LMSLE should get a #GP anyway, no?

Yes, but ideally KVM would explicitly tell the guest "you don't have LMSLE".
Probably a moot point, but at the same time I don't see a reason not to be
explicit.