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

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Message-ID: <ZvcQyAw27hdRZw2B@yury-ThinkPad>
Date: Fri, 27 Sep 2024 13:08:40 -0700
From: Yury Norov <yury.norov@...il.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>
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, Sep 27, 2024 at 12:37:06PM -0700, Linus Torvalds wrote:
> On Fri, 27 Sept 2024 at 09:32, Yury Norov <yury.norov@...il.com> wrote:
> >
> > GENMASK_U128() is a prerequisite needed for arm64 development.
> 
> Note that at least right now, __int128 is marked as conditional for arm64:
> 
>         select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
> 
> which implies that we may have compiler versions that don't actually
> support it at all.
> 
> That said, I'm not sure what those compiler versions might be. Maybe
> this is historical copy-and-paste noise.

Thanks for pointing at this.

So, GCC documentation says that __int128 is an extension, and
CC_HAS_INT128 in init/Kconfig tests for it. All existing code that
uses 128-bit types is protected with the config you mentioned, or
directly with #ifdef __SIZEOF_INT128__. So the GENMASK_U128 should.

I'll drop GENMASK_U128() part from the request and send v2 later today.

Anshuman, can you please make GENMASK_U128() conditional based on
CONFIG_ARCH_SUPPORTS_INT128 and resend?

Thanks,
Yury