linux-kernel - Re: [PATCH] arm64: rust: clean Rust 1.85.0 warning using softfloat target

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Message-ID: <CAGSQo00rWwhcT0SjhUn_e3o+TyCP2stadHwANkmE7-AEeSHBAA@mail.gmail.com>
Date: Tue, 11 Feb 2025 16:57:25 -0800
From: Matthew Maurer <mmaurer@...gle.com>
To: Trevor Gross <tmgross@...ch.edu>
Cc: Miguel Ojeda <ojeda@...nel.org>, Catalin Marinas <catalin.marinas@....com>, 
	Will Deacon <will@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>, 
	moderated for non-subscribers <linux-arm-kernel@...ts.infradead.org>, Boqun Feng <boqun.feng@...il.com>, 
	Gary Guo <gary@...yguo.net>, Björn Roy Baron <bjorn3_gh@...tonmail.com>, 
	Benno Lossin <benno.lossin@...ton.me>, Andreas Hindborg <a.hindborg@...nel.org>, 
	Alice Ryhl <aliceryhl@...gle.com>, rust-for-linux@...r.kernel.org, 
	linux-kernel@...r.kernel.org, patches@...ts.linux.dev, stable@...r.kernel.org, 
	Ralf Jung <post@...fj.de>, Jubilee Young <workingjubilee@...il.com>
Subject: Re: [PATCH] arm64: rust: clean Rust 1.85.0 warning using softfloat target

I successfully booted this on the emulator (with some additional
patches to our system unrelated to this issue), so

Tested-by: Matthew Maurer <mmaurer@...gle.com>


On Tue, Feb 11, 2025 at 3:10 AM Trevor Gross <tmgross@...ch.edu> wrote:
>
> On Mon, Feb 10, 2025 at 10:38 AM Miguel Ojeda <ojeda@...nel.org> wrote:
> >
> > Starting with Rust 1.85.0 (to be released 2025-02-20), `rustc` warns
> > [1] about disabling neon in the aarch64 hardfloat target:
> >
> >     warning: target feature `neon` cannot be toggled with
> >              `-Ctarget-feature`: unsound on hard-float targets
> >              because it changes float ABI
> >       |
> >       = note: this was previously accepted by the compiler but
> >               is being phased out; it will become a hard error
> >               in a future release!
> >       = note: for more information, see issue #116344
> >               <https://github.com/rust-lang/rust/issues/116344>
> >
> > Thus, instead, use the softfloat target instead.
> >
> > While trying it out, I found that the kernel sanitizers were not enabled
> > for that built-in target [2]. Upstream Rust agreed to backport
> > the enablement for the current beta so that it is ready for
> > the 1.85.0 release [3] -- thanks!
> >
> > However, that still means that before Rust 1.85.0, we cannot switch
> > since sanitizers could be in use. Thus conditionally do so.
> >
> > Cc: <stable@...r.kernel.org> # Needed in 6.12.y and 6.13.y only (Rust is pinned in older LTSs).
> > Cc: Catalin Marinas <catalin.marinas@....com>
> > Cc: Will Deacon <will@...nel.org>
> > Cc: Matthew Maurer <mmaurer@...gle.com>
> > Cc: Alice Ryhl <aliceryhl@...gle.com>
> > Cc: Ralf Jung <post@...fj.de>
> > Cc: Jubilee Young <workingjubilee@...il.com>
> > Link: https://github.com/rust-lang/rust/pull/133417 [1]
> > Link: https://rust-lang.zulipchat.com/#narrow/channel/131828-t-compiler/topic/arm64.20neon.20.60-Ctarget-feature.60.20warning/near/495358442 [2]
> > Link: https://github.com/rust-lang/rust/pull/135905 [3]
> > Link: https://github.com/rust-lang/rust/issues/116344
> > Signed-off-by: Miguel Ojeda <ojeda@...nel.org>
>
> This is consistent with what has been discussed for a while on the Rust side.
>
> Reviewed-by: Trevor Gross <tmgross@...ch.edu>