linux-kernel - Re: [GIT PULL] MM updates for 6.14-rc1

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Message-ID: <9312cc52-71d0-405f-b317-3fdccbd998e5@nvidia.com>
Date: Wed, 29 Jan 2025 12:10:06 -0800
From: John Hubbard <jhubbard@...dia.com>
To: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>, Linus Torvalds
	<torvalds@...ux-foundation.org>
CC: Uros Bizjak <ubizjak@...il.com>, Miguel Ojeda <ojeda@...nel.org>, "Andrew
 Morton" <akpm@...ux-foundation.org>, <linux-mm@...ck.org>,
	<mm-commits@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [GIT PULL] MM updates for 6.14-rc1

On 1/26/25 12:58 PM, Miguel Ojeda wrote:
> On Sun, Jan 26, 2025 at 7:30 PM Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
>>
>> That seems to be a reasonable assumption. I guess some crazy setup
>> *could* install a bindgen that uses a different llvm version than
>> rustc itself, but that sounds pretty damn broken.
> 
> Tangential to the issue, but a note on this: we have a few warnings in
> that `rust_is_available.sh` script for things that "do not look
> great", such as bindgen's libclang != Clang when `CC` is Clang, and we
> could have a warning for the case you mention, i.e. bindgen's libclang
> != rustc's LLVM.
> 
> However, currently some kernel developers use toolchains from upstream
> Rust (e.g. from `rustup`) instead of their distributions, so that

Yes, because the distros themselves actually recommended it (Arch Linux,
anyway).

I took a reasonably careful look at the Rust setup for the basics to
build the kernel, for Arch Linux, a couple times, and for 2024 at least,
the answer clearly seemed to be:

     Use the distro's rustup package
         Use rustup to get rustc

     Use the distro's bindgen packaged

Maybe that is All Wrong for 2025+. But this stuff is changing as Rust
and Rust-for-Linux start to settle down, and I'm a little concerned
about warnings unless they warn about something that *really*
matters.

> could be annoying for them (since their bindgen may be picking
> libclang from their distribution).

Trust me, the Rust installation is already sufficiently annoying.
But maybe I'm just being paranoid, and the new warnings will direct
me to a better setup.

I'll take a look at this if you CC me, though, and see how Arch
behaves.

> 
> But eventually when things stabilize more it could make sense, if most
> developers stop using those, as a by-default warning.
> 
> Cheers,
> Miguel
> 

thanks,
-- 
John Hubbard