linux-kernel - Re: [PATCH v1] rust: time: Avoid 64-bit integer division

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Message-Id: <20250503.091412.776716525940008861.fujita.tomonori@gmail.com>
Date: Sat, 03 May 2025 09:14:12 +0900 (JST)
From: FUJITA Tomonori <fujita.tomonori@...il.com>
To: chrisi.schrefl@...il.com
Cc: boqun.feng@...il.com, arnd@...db.de, fujita.tomonori@...il.com,
 rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
 a.hindborg@...sung.com, frederic@...nel.org, lyude@...hat.com,
 tglx@...utronix.de, anna-maria@...utronix.de, jstultz@...gle.com,
 sboyd@...nel.org, ojeda@...nel.org, alex.gaynor@...il.com,
 gary@...yguo.net, bjorn3_gh@...tonmail.com, benno.lossin@...ton.me,
 aliceryhl@...gle.com, tmgross@...ch.edu, linux@...linux.org.uk
Subject: Re: [PATCH v1] rust: time: Avoid 64-bit integer division

On Fri, 2 May 2025 01:38:43 +0200
Christian Schrefl <chrisi.schrefl@...il.com> wrote:

>>> What is Arm specific here? I'm not aware of the compiler doing anything
>> 
>> Because Arm is the only 32bit architecture that selects CONFIG_HAVE_RUST
>> for non-UML cases, i.e. this is the only 32bit architecture that has
>> this problem. If your point is we should do this for all 32bit
>> architectures, then I won't disagree. Just s/CONFIG_ARM/CONFIG_32BIT
>> then.
> 
> I would be for using `CONFIG_32BIT` since from what I understand this
> applies to all 32bit architectures. It feels a bit weird to single out
> arm just because it is the only one that currently has rust support.

CONFIG_32BIT doesn't work because 32-bit ARM doesn't set it. I use
CONFIG_64BIT, enabled on all 64-bit architectures supported by Rust.

https://lore.kernel.org/lkml/20250502004524.230553-1-fujita.tomonori@gmail.com/

Unlike CONFIG_ARM, the intention behind CONFIG_64BIT is clear, so I
also think it's the better choice.

Thanks!