linux-kernel - Re: [PATCH -tip] x86/locking/atomic: Use asm

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250305194003.GA35526@noisy.programming.kicks-ass.net>
Date: Wed, 5 Mar 2025 20:40:03 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Linus Torvalds <torvalds@...uxfoundation.org>
Cc: Uros Bizjak <ubizjak@...il.com>, Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...el.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH -tip] x86/locking/atomic: Use asm_inline for atomic
 locking insns

On Wed, Mar 05, 2025 at 07:04:08AM -1000, Linus Torvalds wrote:
> And honestly, none of that makes sense any more. You can't buy a UP
> machine any more, and the only UP case would be some silly minimal
> virtual environment, and if people really care about that minimal
> case, they should just compile the kernel without SMP support.
> Becxause UP has gone from being the default to being irrelevant. At
> least for x86-64.
> 
> So I think we should just get rid of LOCK_PREFIX_HERE and the
> smp_locks section entirely.
> 
> Which would probably obviate the need for your patch, since then the
> compiler wouldn't see it as some big instruction. But your patch isn't
> wrong, so this is absolutely not a NAK, more of a "we should go
> further".
> 
> Hmm?

I'm all for removing that.

On that note, a number of architectures have already made the next step
and that is mandate SMP=y.

The down-side of that it that it would make a definite dent in the
compile coverage for SMP=n code -- but perhaps we have enough robots to
get away with that.