linux-kernel - Re: [PATCH v4 1/6] x86/bugs: Add asm helpers for executing VERW

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Message-ID: <20231201200442.lvyep5uqc6oa7kwj@treble>
Date:   Fri, 1 Dec 2023 12:04:42 -0800
From:   Josh Poimboeuf <jpoimboe@...nel.org>
To:     Andrew Cooper <andrew.cooper3@...rix.com>
Cc:     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>,
        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,
        Nikolay Borisov <nik.borisov@...e.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,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alyssa Milburn <alyssa.milburn@...el.com>
Subject: Re: [PATCH v4 1/6] x86/bugs: Add asm helpers for executing VERW

On Fri, Dec 01, 2023 at 07:39:05PM +0000, Andrew Cooper wrote:
> On 01/12/2023 7:36 pm, Josh Poimboeuf wrote:
> > On Fri, Oct 27, 2023 at 07:38:40AM -0700, Pawan Gupta wrote:
> >> +.pushsection .entry.text, "ax"
> >> +
> >> +.align L1_CACHE_BYTES, 0xcc
> >> +SYM_CODE_START_NOALIGN(mds_verw_sel)
> >> +	UNWIND_HINT_UNDEFINED
> >> +	ANNOTATE_NOENDBR
> >> +	.word __KERNEL_DS
> >> +.align L1_CACHE_BYTES, 0xcc
> >> +SYM_CODE_END(mds_verw_sel);
> >> +/* For KVM */
> >> +EXPORT_SYMBOL_GPL(mds_verw_sel);
> >> +
> >> +.popsection
> > This is data, so why is it "CODE" in .entry.text?
> 
> Because KPTI.

Urgh... Pawan please add a comment.

-- 
Josh