linux-kernel - Re: [PATCH v2 5/6] KVM: VMX: Use BT+JNC, i.e. EFLAGS.CF to select VMRESUME vs. VMLAUNCH

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Message-ID: <dccdd1e1-0ae9-448a-aa2f-aa3f7b988559@suse.com>
Date:   Wed, 25 Oct 2023 11:15:15 +0300
From:   Nikolay Borisov <nik.borisov@...e.com>
To:     Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        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>,
        Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>, tony.luck@...el.com,
        ak@...ux.intel.com, tim.c.chen@...ux.intel.com
Cc:     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 v2 5/6] KVM: VMX: Use BT+JNC, i.e. EFLAGS.CF to select
 VMRESUME vs. VMLAUNCH



On 24.10.23 г. 11:08 ч., Pawan Gupta wrote:
> From: Sean Christopherson <seanjc@...gle.com>
> 
> Use EFLAGS.CF instead of EFLAGS.ZF to track whether to use VMRESUME versus
> VMLAUNCH.  Freeing up EFLAGS.ZF will allow doing VERW, which clobbers ZF,
> for MDS mitigations as late as possible without needing to duplicate VERW
> for both paths.
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> Signed-off-by: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>

Reviewed-by: Nikolay Borisov <nik.borisov@...e.com>