linux-kernel - Re: [PATCH] x86/kexec: Add a comment to relocate

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Message-ID: <20230607111957.sppocwpkhfb2e2vf@box.shutemov.name>
Date:   Wed, 7 Jun 2023 14:19:57 +0300
From:   kirill.shutemov@...ux.intel.com
To:     Kai Huang <kai.huang@...el.com>
Cc:     linux-kernel@...r.kernel.org, dave.hansen@...ux.intel.com,
        peterz@...radead.org, hpa@...or.com, konrad.wilk@...cle.com,
        rostedt@...dmis.org, jpoimboe@...nel.org
Subject: Re: [PATCH] x86/kexec: Add a comment to relocate_kernel() for better
 readability

On Wed, Jun 07, 2023 at 10:39:10PM +1200, Kai Huang wrote:
> The reason to save %rcx to %r11 before calling swap_pages isn't that
> obvious w/o looking into the swap_pages itself.  Add a comment to
> improve the readability.
> 
> Signed-off-by: Kai Huang <kai.huang@...el.com>
> ---
>  arch/x86/kernel/relocate_kernel_64.S | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S
> index 56cab1bb25f5..97deae3c5e6c 100644
> --- a/arch/x86/kernel/relocate_kernel_64.S
> +++ b/arch/x86/kernel/relocate_kernel_64.S
> @@ -169,6 +169,10 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
>  	wbinvd
>  1:
>  
> +	/*
> +	 * Save the preserve_context to %r11 as
> +	 * swap_pages clobbers %rcx.
> +	 */

Line split is not needed. It fits nicely under 80-characters.

+	/* Save the preserve_context to %r11 as swap_pages clobbers %rcx. */

Otherwise, LGTM.

>  	movq	%rcx, %r11
>  	call	swap_pages
>  
> 
> base-commit: 409bf2895d71bb68bc5b8589036e5ed1ca30bada
> -- 
> 2.40.1
> 

-- 
  Kiryl Shutsemau / Kirill A. Shutemov