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

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Date:   Wed, 21 Sep 2022 18:06:34 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Jim Mattson <jmattson@...gle.com>
Cc:     Sean Christopherson <seanjc@...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 Wed, Sep 21, 2022 at 08:11:29AM -0700, Jim Mattson wrote:
> Yes, after the revert, KVM will treat the bit as reserved, and it will
> synthesize a #GP, *in violation of the architectural specification.*

Architectural, schmarchitectural... Intel hasn't implemented it so meh.

> KVM can't just decide willy nilly to reserve arbitrary bits. If it is
> in violation of AMD's architectural specification, the virtual CPU is
> defective.

Grrr, after your revert that this bit was *only* reserved and nothing
else to KVM. Like every other reserved bit in EFER. Yeah, yeah, AMD
specified it as architectural but Intel didn't implement it so there's
this thing on paper and there's reality...

Anyway, enough about this - we're on the same page.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette