linux-kernel - Re: [PATCH 14/20] x86/barrier: Use alternative

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Message-ID: <CAHk-=wjtvTPERDdrok2kDrSSFBjqHCCNVff95VVxhvP6wCC6jg@mail.gmail.com>
Date: Fri, 14 Mar 2025 13:49:48 -1000
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Josh Poimboeuf <jpoimboe@...nel.org>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, 
	Peter Zijlstra <peterz@...radead.org>, Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>, 
	Uros Bizjak <ubizjak@...il.com>, Andrew Cooper <andrew.cooper3@...rix.com>, 
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH 14/20] x86/barrier: Use alternative_io() in 32-bit barrier functions

On Fri, 14 Mar 2025 at 11:42, Josh Poimboeuf <jpoimboe@...nel.org> wrote:
>
> +#define mb() alternative_io("lock addl $0,-4(%%esp)",                  \
> +                           "mfence", X86_FEATURE_XMM2,                 \
> +                           ARG(),                                      \
> +                           ARG(),                                      \
> +                           ARG("memory", "cc"))

So all of these patches look like good cleanups to me, but I do wonder
if we should

 (a) not use some naming *quite* as generic as 'ARG()'

 (b) make the asms use ARG_OUT/ARG_IN/ARG_CLOBBER() to clarify

because that ARG(), ARG(), ARGC() pattern looks odd to me.

Maybe it's just me.

Regardless, I do think the series looks like a nice improvement even
in the current form, even if that particular repeated pattern feels
strange.

              Linus