linux-kernel - Re: [PATCH v3 6/6] KVM: VMX: Move VERW closer to VMentry for MDS mitigation

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Date:   Thu, 26 Oct 2023 14:27:21 -0700
From:   Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Jonathan Corbet <corbet@....net>,
        Paolo Bonzini <pbonzini@...hat.com>, tony.luck@...el.com,
        ak@...ux.intel.com, tim.c.chen@...ux.intel.com,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        kvm@...r.kernel.org,
        Alyssa Milburn <alyssa.milburn@...ux.intel.com>,
        Daniel Sneddon <daniel.sneddon@...ux.intel.com>,
        antonio.gomez.iglesias@...ux.intel.com
Subject: Re: [PATCH  v3 6/6] KVM: VMX: Move VERW closer to VMentry for MDS
 mitigation

On Thu, Oct 26, 2023 at 01:17:47PM -0700, Sean Christopherson wrote:
> Alternatively, and maybe even preferably, this would make it more obvious that
> the two are mutually exclusive and would also be a (very, very) small perf win
> when the mitigation is enabled.

Agree.

> -       vmx_disable_fb_clear(vmx);
> +       if (!cpu_feature_enabled(X86_FEATURE_CLEAR_CPU_BUF))
> +               vmx_disable_fb_clear(vmx);