linux-kernel - Re: [PATCHv6 03/16] x86/alternatives: Disable LASS when patching kernel alternatives

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Message-ID: <kal5vsl6lpxo4ygli4yj2y5cqrosh2qxm5buxoh6d6ba4dloqe@nkxti3f7vrhj>
Date: Fri, 20 Jun 2025 20:18:56 +0300
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Dave Hansen <dave.hansen@...el.com>
Cc: Andy Lutomirski <luto@...nel.org>, 
	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>, Ard Biesheuvel <ardb@...nel.org>, 
	"Paul E. McKenney" <paulmck@...nel.org>, Josh Poimboeuf <jpoimboe@...nel.org>, 
	Xiongwei Song <xiongwei.song@...driver.com>, Xin Li <xin3.li@...el.com>, 
	"Mike Rapoport (IBM)" <rppt@...nel.org>, Brijesh Singh <brijesh.singh@....com>, 
	Michael Roth <michael.roth@....com>, Tony Luck <tony.luck@...el.com>, 
	Alexey Kardashevskiy <aik@....com>, Alexander Shishkin <alexander.shishkin@...ux.intel.com>, 
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	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org, 
	linux-mm@...ck.org
Subject: Re: [PATCHv6 03/16] x86/alternatives: Disable LASS when patching
 kernel alternatives

On Fri, Jun 20, 2025 at 08:33:57AM -0700, Dave Hansen wrote:
> On 6/20/25 06:53, Kirill A. Shutemov wrote:
> > +/*
> > + * poking_init() initializes the text poking address from the lower half of the
> > + * address space. Relax LASS enforcement when accessing the poking address.
> > + */
> 
> This does not read quite right. I think there's some unnecessary
> confusiuon about initializing the address versus the contents. But
> either way, how about:
> 
> /*
>  * Text poking creates and uses a mapping in the lower half of the
>  * address space. Relax LASS enforcement when accessing the poking
>  * address.
>  */

Looks good. Will update, thanks!
> 
> >  static void text_poke_memset(void *dst, const void *src, size_t len)
> >  {
> >  	int c = *(const int *)src;
> >  
> > -	memset(dst, c, len);
> > +	lass_stac();
> > +	__inline_memset(dst, c, len);
> > +	lass_clac();
> >  }
> 
> Yeah, this patch small enough that lass_{stac,clac}() are definitely
> misplaced in this series. Just move them into this patch.

Okay, makes sense.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov