Re: [PATCH 4/4] s390: enable Rust support

[Miguel Ojeda]

On Mon, May 18, 2026 at 5:19 PM Jan Polensky <japo@xxxxxxxxxxxxx> wrote:
>
> thanks for the review.

You're welcome!

> -Zpacked-stack: I’m not aware of a dedicated rust-lang/rust tracking
> issue for this flag. The implementation landed via rust-lang/rust PR
> 152432, but it doesn’t appear to reference a tracking issue.

Yeah, #152432 is the one I linked in our live list.

Sometimes tracking issues are missing, but I think upstream Rust is
generally OK adding them -- I have created one, tagged and linked it,
please feel free to modify it, close it, etc. if needed:

  https://github.com/rust-lang/rust/issues/156724

I hope that helps.

> minimum toolchain version / beta: as long as we pass -Zpacked-stack in
> KBUILD_RUSTFLAGS, we need a nightly compiler; beta/stable won’t accept -Z
> flags. In v2 I’ll drop the 1.97.0-nightly guess and set the minimum to
> 1.96.0-nightly (the first release line that includes -Zpacked-stack).
> We’ll keep the “-nightly” suffix while this remains a -Z flag. If it gets
> stabilized and nothing blocks, the earliest stable release that could
> plausibly carry it would be 1.98.

No, it is meant to work -- we use `-Z` flags (and other unstable
features) on a regular basis, as you can see in our issue #2 that I
linked above, e.g. you can see some of them with:

  git grep '\-Z' Makefile

Please see:

  https://rust-for-linux.com/unstable-features

for some more details.

That is why I was suggesting that you test the current beta, because
it will become soon 1.96. If it doesn't, then it would be wise to try
to see why it doesn't! :)

Thanks!

Cheers,
Miguel