linux-kernel - Re: [PATCH] x86/asm: Use asm_inline() instead of asm() in amd_clear

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Message-ID: <Z9QCRydO2yiCq_YR@gmail.com>
Date: Fri, 14 Mar 2025 11:17:43 +0100
From: Ingo Molnar <mingo@...nel.org>
To: Borislav Petkov <bp@...en8.de>
Cc: Uros Bizjak <ubizjak@...il.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [PATCH] x86/asm: Use asm_inline() instead of asm() in
 amd_clear_divider()


* Ingo Molnar <mingo@...nel.org> wrote:

> 
> * Borislav Petkov <bp@...en8.de> wrote:
> 
> > Sorry but this doesn't justify this churn. There's nothing 
> > quantifyingly palpable here to warrant this.
> 
> I disagree, asm() is a known-bad inlining interface for fundamentally 
> single-instruction inlines like this one, and there's various 
> performance benefits to cleaning this up, as evidenced by the benchmark 
> numbers and analysis in this pending commit:
> 
>   9628d19e91f1 ("x86/locking/atomic: Improve performance by using asm_inline() for atomic locking instructions")

Here's a link for those who'd like to view this via the web:

  https://lore.kernel.org/all/174188884263.14745.1542926632284353047.tip-bot2@tip-bot2/

Thanks,

	Ingo