linux-kernel - Re: [tip: x86/asm] x86/asm: Make ASM_CALL_CONSTRAINT conditional on frame pointers

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Message-ID: <CAHk-=wjc8jnsOkLq1YfmM0eQqceyTunLEcfpXcm1EBhCDaLLgg@mail.gmail.com>
Date: Tue, 4 Mar 2025 08:01:58 -1000
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Ingo Molnar <mingo@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-tip-commits@...r.kernel.org, 
	Josh Poimboeuf <jpoimboe@...nel.org>, "Peter Zijlstra (Intel)" <peterz@...radead.org>, 
	Brian Gerst <brgerst@...il.com>, "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org
Subject: Re: [tip: x86/asm] x86/asm: Make ASM_CALL_CONSTRAINT conditional on
 frame pointers

On Tue, 4 Mar 2025 at 07:51, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> Put another way: the old code has years of testing and is
> significantly simpler. The new code is new and untested and more
> complicated and has already caused known new problems, never mind any
> unknown ones.
>
> It really doesn't sound like a good trade-off to me.

Side note: it's not clear that we should need to do that
ASM_CALL_CONSTRAINT thing _at_all_ any more.

Iirc, the only reason we did it was for old versions of gcc, and we're
already in the process of switching minimum gcc versions up to past
where the whole thing is relevant at all. There's another tip bot
commit that makes the minimum gcc version be 8.1 due to the (much
MUCH) cleaner percpu section series.

And afaik, that makes all of this completely pointless.

So tell me again - why are we making the kernel code worse?

                Linus