Re: [PATCH v3 4/4] s390: Enable Rust support

[Alice Ryhl <aliceryhl@google.com>]

On Thu, May 21, 2026 at 06:56:22PM +0200, Jan Polensky wrote:
> Enable building Rust code on s390 by wiring the architecture into the
> kernel Rust infrastructure.
> 
> Add s390 to the Rust arch support documentation, provide the s390 Rust
> target and required compiler flags, and set the bindgen target for
> arch/s390. Adjust the Rust target generation and minimum rustc version
> gating so the s390 setup is handled explicitly.
> 
> The Rust toolchain uses the "s390x" triple naming for the 64 bit target.
> 
> Rust support is currently incompatible with CONFIG_EXPOLINE, which
> relies on compiler support for the -mindirect-branch= and
> -mfunction_return= options. Therefore, select HAVE_RUST only when
> EXPOLINE is disabled.
> 
> Signed-off-by: Jan Polensky <japo@linux.ibm.com>

> diff --git a/scripts/min-tool-version.sh b/scripts/min-tool-version.sh
> index b96ec2d379b6..296acf8f71aa 100755
> --- a/scripts/min-tool-version.sh
> +++ b/scripts/min-tool-version.sh
> @@ -31,7 +31,11 @@ llvm)
>  	fi
>  	;;
>  rustc)
> -	echo 1.85.0
> +	if [ "$SRCARCH" = "s390" ]; then
> +		echo 1.96.0
> +	else
> +		echo 1.85.0
> +	fi

For other version constraints we have listed them in the Kconfig file to
guard the select HAVE_RUST or similar annotations instead of here. Is
this the best place to add this constraint?

Alice