linux-kernel - Re: [PATCH 2/5] KVM: svm: Disallow EFER.LMSLE on hardware that doesn't support it

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Message-ID: <YydrsMjAF5zjqTGK@zn.tnic>
Date:   Sun, 18 Sep 2022 21:04:16 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Jim Mattson <jmattson@...gle.com>, Avi Kivity <avi@...hat.com>,
        Babu Moger <babu.moger@....com>,
        "Chang S. Bae" <chang.seok.bae@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Joerg Roedel <joerg.roedel@....com>,
        Josh Poimboeuf <jpoimboe@...nel.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Wyes Karny <wyes.karny@....com>, x86@...nel.org
Subject: Re: [PATCH 2/5] KVM: svm: Disallow EFER.LMSLE on hardware that
 doesn't support it

On Fri, Sep 16, 2022 at 10:33:29PM +0000, Sean Christopherson wrote:
> ...
> Either way, KVM appears to be carrying a half-baked "fix" for a buggy guest that's
> long since gone.  So like we did in commit 8805875aa473 ("Revert "KVM: nVMX: Do not
> expose MPX VMX controls when guest MPX disabled""), I think we should just revert
> the "fix".

If, as message 0/5 says, setting this bit so that SLE11 Xen 4.0 boots as
a nested hypervisor is the use case, then sure, unconditional NO_LSMLE
and we all should go on with our lives.

-- 
Regards/Gruss,
    Boris.

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