linux-kernel - Re: [PATCH 16/20] x86/cpu: Use alternative_io() in amd_clear

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Message-ID: <CAFULd4ZJiYyaAJPm0Dg1VeF1q9uw54CCzz2WQ4ufPhJ46PXfkA@mail.gmail.com>
Date: Sat, 15 Mar 2025 10:03:27 +0100
From: Uros Bizjak <ubizjak@...il.com>
To: Josh Poimboeuf <jpoimboe@...nel.org>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, 
	Linus Torvalds <torvalds@...ux-foundation.org>, Peter Zijlstra <peterz@...radead.org>, 
	Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>, Andrew Cooper <andrew.cooper3@...rix.com>, 
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH 16/20] x86/cpu: Use alternative_io() in amd_clear_divider()

On Fri, Mar 14, 2025 at 10:42 PM Josh Poimboeuf <jpoimboe@...nel.org> wrote:
>
> Use the standard alternative_io() interface.
>
> Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
> ---
>  arch/x86/include/asm/processor.h | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
> index b458ff0e4c79..d7f3f03594a2 100644
> --- a/arch/x86/include/asm/processor.h
> +++ b/arch/x86/include/asm/processor.h
> @@ -709,8 +709,10 @@ static inline u32 per_cpu_l2c_id(unsigned int cpu)
>   */
>  static __always_inline void amd_clear_divider(void)
>  {
> -       asm volatile(ALTERNATIVE("", "div %[one]\n\t", X86_BUG_DIV0)
> -                    :: "a" (0), "d" (0), [one] "r" (1));
> +       alternative_io("",
> +                      "div %[one]\n\t", X86_BUG_DIV0,

A nit - can the above be in one line? Also no need for a trailing \n\t.

Thanks,
Uros.