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

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Message-ID: <20231220011535.cw3smza3kb5resji@desk>
Date: Tue, 19 Dec 2023 17:15:35 -0800
From: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
To: Josh Poimboeuf <jpoimboe@...nel.org>
Cc: Andrew Cooper <andrew.cooper3@...rix.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 12:04:42PM -0800, Josh Poimboeuf wrote:
> 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.

Yes, this place needs a comment, will add.