linux-kernel - Re: [PATCH RESEND] x86/asm: Use inout "+" asm onstraint modifiers in __iowrite32

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Message-ID: <553f1a09-0269-46bc-8d39-20e67bef0b59@zytor.com>
Date: Tue, 20 Jan 2026 12:51:49 -0800
From: "H. Peter Anvin" <hpa@...or.com>
To: Uros Bizjak <ubizjak@...il.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: [PATCH RESEND] x86/asm: Use inout "+" asm onstraint modifiers in
 __iowrite32_copy()

On 2025-11-10 14:31, Uros Bizjak wrote:
> Use inout "+" asm constraint modifiers to simplify asm operands.
> 
> No functional changes intended.
> 
> Signed-off-by: Uros Bizjak <ubizjak@...il.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...nel.org>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> ---
>  arch/x86/include/asm/io.h | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)

Looks good to me.

Reviewed-by: H. Peter Anvin (Intel) <hpa@...or.com>

> diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
> index ca309a3227c7..2ea25745e059 100644
> --- a/arch/x86/include/asm/io.h
> +++ b/arch/x86/include/asm/io.h
> @@ -218,9 +218,8 @@ static inline void __iowrite32_copy(void __iomem *to, const void *from,
>  				    size_t count)
>  {
>  	asm volatile("rep movsl"
> -		     : "=&c"(count), "=&D"(to), "=&S"(from)
> -		     : "0"(count), "1"(to), "2"(from)
> -		     : "memory");
> +		     : "+D"(to), "+S"(from), "+c"(count)
> +		     : : "memory");
>  }
>  #define __iowrite32_copy __iowrite32_copy
>  #endif