Re: [PATCH v3 0/4] s390: Enable Rust support and add required arch glue

[Alice Ryhl <aliceryhl@google.com>]

On Wed, May 27, 2026 at 12:08:38PM +0200, Miguel Ojeda wrote:
> On Tue, May 26, 2026 at 6:13 PM Heiko Carstens <hca@linux.ibm.com> wrote:
> >
> > An Ack from you would be appreciated, even though you made it already
> > clear that this series looks ok.
> 
> I did a quick `LLVM=1` test and booted it in QEMU. That worked and I
> could see the KUnit tests, though we get the:
> 
>   warning: unstable feature specified for `-Ctarget-feature`: `backchain`
> 
> But I assume you are OK with that for now (and if you are, then
> avoiding a custom target is worth it, I would say).

Based on some very quick research, it looks like enabling the backchain
target feature does not affect the ABI in the sense that mixing together
object files with and without this option will still work. If that's the
case, we can add this to the list of known target features for this
target in rustc, which will silence this warning.

(If it affects the ABI in a breaking manner, it needs to be added as a
separate flag rather than being added as part of the -Ctarget-feature
flag.)

Alice