linux-kernel - Re: arch/x86/include/asm/cmpxchg_32.h:149:9: error: inline assembly requires more registers than available

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Message-ID: <CAHk-=whPqqZVSeJiQsMvsAxtAmtR9iAuB4gg_1sUK2D-uBPpLw@mail.gmail.com>
Date: Sun, 23 Jun 2024 14:07:37 -0400
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Uros Bizjak <ubizjak@...il.com>
Cc: kernel test robot <lkp@...el.com>, oe-kbuild-all@...ts.linux.dev, 
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>, 
	Borislav Petkov <bp@...en8.de>, Peter Zijlstra <peterz@...radead.org>
Subject: Re: arch/x86/include/asm/cmpxchg_32.h:149:9: error: inline assembly
 requires more registers than available

On Sun, 23 Jun 2024 at 13:48, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> Now, from having looked a bit at this, I can point you to the
> differences introduced by having to have the emulation fallback.

Ahh.

Itr does all the same things *and* it has

    "S" (_ptr)

as an added register pressure, because if we take the "call
cmpxchg8b_emu", we need the address in a fixed place.

I don't see any immediately obvious workaround.

              Linus