Hi all,

On 02.03.26 08:29, Alice Ryhl wrote:

On Mon, Mar 02, 2026 at 11:25:54AM +0530, Mukesh Kumar Chaurasiya wrote:

quoted

On Tue, Feb 24, 2026 at 09:58:10AM +0100, Ralf Jung wrote:

quoted

Hi all,

On 23.02.26 16:31, Miguel Ojeda wrote:

quoted

On Mon, Feb 23, 2026 at 3:26 AM Mukesh Kumar Chaurasiya
[off-list ref] wrote:

quoted

I think, disabling altivec, fpu and vsx with compiler flag will work.

What are your opinion on this?

It is really up to upstream Rust -- for us, i.e. the kernel, it
usually doesn't really matter much how things like that are
accomplished: whether via flags, a built-in target, a custom target,
etc. However, we need to know what the path to stability is.

My understanding (but I may be wrong) is that upstream Rust prefer we
use built-in targets for softfloat instead of disabling via
`-Ctarget-feature` (and that the other options may go away soon and/or
will never be stable) -- at least for some cases. For instance, for
arm64, please this recent change kernel-side regarding `neon` as an
entry point:

    446a8351f160 ("arm64: rust: clean Rust 1.85.0 warning using softfloat target")

So please ask upstream Rust (probably in their Zulip, e.g. in
t-compiler or rust-for-linux channels) what you should do for powerpc.
They will likely be happy with a PR adding the target (or whatever
they decide) as Alice mentions. And until we reach that minimum
version (in a year or more), we can use something else meanwhile. But
at least we will have a way towards the end goal, if that makes sense.

In case it helps, let me Cc Ralf, Jubilee and Matthew who were
involved in some of that discussion in the past, plus the compiler
leads.

Upstream Rust dev here. Indeed we'd strongly prefer if this could use a
built-in Rust target; we can work with you on adding a new target if that is
needed.
The kernel currently uses a custom JSON target on x86 and that's quite the
headache for compiler development: JSON targets are highly unstable and
directly expose low-level details of how the compiler internally represents
targets. When we change that representation, we update all built-in targets,
but of course we cannot update JSON targets. So whenever possible we'd like
to move towards reducing the number of JSON targets used by the kernel, not
increase it. :)

Kind regards,
Ralf

Hey,

Sorry for delayed response. I was out of network zone.

I am not sure about the process of how to get this in rust toolchain.
Should I raise an issue of github for this?

You would need to add a new file to compiler/rustc_target/src/spec/targets
in the rustc repository.

If you're not sure what to put there, I would suggest coming up with
something that looks plausible, and opening a PR with that. Then others
can help you with filling out the target correctly.

Also see the documentation at 
<https://doc.rust-lang.org/rustc/target-tier-policy.html#adding-a-new-target>.

Kind regards,
Ralf