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

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Date:   Fri, 1 Dec 2023 19:39:05 +0000
From:   Andrew Cooper <andrew.cooper3@...rix.com>
To:     Josh Poimboeuf <jpoimboe@...nel.org>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.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>,
        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 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.

~Andrew