linux-kernel - Re: [PATCH v2 14/15] x86/lib/memmove_64.S: Convert memmove() to ALTERNATIVE macro

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Message-ID: <20150304071949.GA22014@gmail.com>
Date:	Wed, 4 Mar 2015 08:19:49 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Borislav Petkov <bp@...en8.de>
Cc:	X86 ML <x86@...nel.org>, Andy Lutomirski <luto@...capital.net>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 14/15] x86/lib/memmove_64.S: Convert memmove() to
 ALTERNATIVE macro


* Borislav Petkov <bp@...en8.de> wrote:

> From: Borislav Petkov <bp@...e.de>
> 
> Make it execute the ERMS version if support is present and we're in the
> forward memmove() part and remove the unfolded alternatives section
> definition.
> 
> Signed-off-by: Borislav Petkov <bp@...e.de>
> ---
>  arch/x86/lib/memmove_64.S | 19 ++-----------------
>  1 file changed, 2 insertions(+), 17 deletions(-)
> 
> diff --git a/arch/x86/lib/memmove_64.S b/arch/x86/lib/memmove_64.S
> index bbfa6b269ece..0f8a0d0331b9 100644
> --- a/arch/x86/lib/memmove_64.S
> +++ b/arch/x86/lib/memmove_64.S
> @@ -5,7 +5,6 @@
>   * This assembly file is re-written from memmove_64.c file.
>   *	- Copyright 2011 Fenghua Yu <fenghua.yu@...el.com>
>   */
> -#define _STRING_C
>  #include <linux/linkage.h>
>  #include <asm/dwarf2.h>
>  #include <asm/cpufeature.h>
> @@ -44,6 +43,8 @@ ENTRY(__memmove)
>  	jg 2f
>  
>  .Lmemmove_begin_forward:
> +	ALTERNATIVE "", "movq %rdx, %rcx; rep movsb; retq", X86_FEATURE_ERMS
> +
>  	/*
>  	 * movsq instruction have many startup latency
>  	 * so we handle small size by general register.

Btw., it might make sense to translate that comment to English, while 
at it? (in a separate patch)

Thanks,

	Ingo
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