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From: Ard Biesheuvel <ardb@kernel.org>
Date: Wed, 5 Jun 2024 19:59:37 +0200
Message-ID: <CAMj1kXHa58Zcq3extXw4VXGnpVHbd5urzCGnh_oCo-BLMxMrJQ@mail.gmail.com>
Subject: Re: [PATCH] arch: um: rust: Add i386 support for Rust
To: Nathan Chancellor <nathan@kernel.org>
Cc: David Gow <davidgow@google.com>, Brendan Higgins <brendan.higgins@linux.dev>, 
	Rae Moar <rmoar@google.com>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, 
	Miguel Ojeda <ojeda@kernel.org>, "H . Peter Anvin" <hpa@zytor.com>, Masahiro Yamada <masahiroy@kernel.org>, 
	Richard Weinberger <richard@nod.at>, Anton Ivanov <anton.ivanov@cambridgegreys.com>, 
	Johannes Berg <johannes@sipsolutions.net>, kunit-dev@googlegroups.com, 
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	Boqun Feng <boqun.feng@gmail.com>, Gary Guo <gary@garyguo.net>, 
	=?UTF-8?Q?Bj=C3=B6rn_Roy_Baron?= <bjorn3_gh@protonmail.com>, 
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On Wed, 5 Jun 2024 at 08:22, Nathan Chancellor <nathan@kernel.org> wrote:
>
> Hi David,
>
> Just a fly by comment on style, I don't have much to say content :)
>
> On Wed, Jun 05, 2024 at 06:40:50AM +0800, David Gow wrote:
> > At present, Rust in the kernel only supports 64-bit x86, so UML has
> > followed suit. However, it's significantly easier to support 32-bit i386
> > on UML than on bare metal, as UML does not use the -mregparm option
> > (which alters the ABI), which is not yet supported by rustc[1].
> >
> > Add support for CONFIG_RUST on um/i386, by adding a new target config to
> > generate_rust_target, and replacing various checks on CONFIG_X86_64 to
> > also probably like  support CONFIG_X86_32.
> >
> > We still use generate_rust_target, rather than a built-in rustc target,
> > in oPrder to match x86_64, provide a future place for -mregparm, and more
> > easily disable floating point instructions.
> >
> > With these changes, the KUnit tests pass with:
> > kunit.py run --make_options LLVM=1 --kconfig_add CONFIG_RUST=y
> > --kconfig_add CONFIG_64BIT=n --kconfig_add CONFIG_FORTIFY_SOURCE=n
> >
> > An earlier version of these changes was proposed on the Rust-for-Linux
> > github[2].
> >
> > [1]: https://github.com/rust-lang/rust/issues/116972
> > [2]: https://github.com/Rust-for-Linux/linux/pull/966
> >
> > Signed-off-by: David Gow <davidgow@google.com>
> ...
> > -ifdef CONFIG_X86_64
> > +ifneq ($(or $(CONFIG_X86_64),$(CONFIG_X86_32)),)
>
> These configurations are mutually exclusive, so would it look more
> readable to have it be:
>
>
> ifeq ($(CONFIG_X86_32)$(CONFIG_X86_64),y)
>

Or simply

ifdef CONFIG_X86