linux-kernel - Re: [GIT PULL] bitmap changes for v6.12-rc1

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Message-ID: <CAHk-=whTUzTm9NjxBYvp0Bv3cT4YuFKAmOVQAX44f8JaaxoT5g@mail.gmail.com>
Date: Fri, 27 Sep 2024 13:29:34 -0700
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Yury Norov <yury.norov@...il.com>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, 
	Rasmus Villemoes <linux@...musvillemoes.dk>, Anshuman Khandual <anshuman.khandual@....com>, 
	Brian Norris <briannorris@...omium.org>
Subject: Re: [GIT PULL] bitmap changes for v6.12-rc1

On Fri, 27 Sept 2024 at 13:08, Yury Norov <yury.norov@...il.com> wrote:
>
> I'll drop GENMASK_U128() part from the request and send v2 later today.

I took your pull request, because I _suspect_ the test for
CC_HAS_INT128 is historical.

I *think* all the gcc (and clang) versions we support has __int128
support on arm64.  It's not a new feature.

That said, I'm not *sure* about it. The fact that we have a test for
it in the arm64 Kconfig file may be because we actually have compilers
that don't support __int128. Or it might be due to entirely historical
reasons.

So my point was just that people who make use of this should really be
aware of this worry, and double-check.

GENMASK_U128() is not necessarily wrong. It's just that it's not
necessarily available everywhere (it most definitely isn't on most
32-bit targets, for example, but arm64 _may_ be always ok).

               Linus