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

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Message-ID: <15335559-bbb2-4da1-bbb9-878edf05437c@intel.com>
Date: Fri, 20 Jun 2025 08:33:57 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
 Andy Lutomirski <luto@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
 Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
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 "H. Peter Anvin" <hpa@...or.com>, Peter Zijlstra <peterz@...radead.org>,
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 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>,
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Cc: Jonathan Corbet <corbet@....net>, Sohil Mehta <sohil.mehta@...el.com>,
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 Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
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Subject: Re: [PATCHv6 03/16] x86/alternatives: Disable LASS when patching
 kernel alternatives

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.
 */

>  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.