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([2001:871:22a:99c5::1ad1]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ac7bfee2591sm468902666b.79.2025.04.05.13.05.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 05 Apr 2025 13:05:21 -0700 (PDT) Message-ID: <399cceb4-dcf5-4af8-a8b7-6741e9b7e8ae@gmail.com> Date: Sat, 5 Apr 2025 22:05:19 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] arm: rust: Enable Rust support for ARMv7 To: Linus Walleij Cc: Miguel Ojeda , Alex Gaynor , Boqun Feng , Gary Guo , =?UTF-8?Q?Bj=C3=B6rn_Roy_Baron?= , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Jonathan Corbet , Russell King , Rudraksha Gupta , Ard Biesheuvel , Geert Stappers , Andrew Lunn , Jamie Cunliffe , Sven Van Asbroeck , rust-for-linux@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org References: <20250123-rfl-arm32-v3-1-8f13623d42c5@gmail.com> Content-Language: en-US, de-DE From: Christian Schrefl In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Hi Linus, On 21.03.25 8:24 AM, Linus Walleij wrote: > Hi Christian, > > thanks for your patch! > > Sorry for being late to the show. I missed this very nice patch > that was actually on my personal TODO but I have to much > to do and also I'm not smart with Rust, but I'm a big supporter. > > On Thu, Jan 23, 2025 at 11:40 PM Christian Schrefl > wrote: > >> + select HAVE_RUST if CPU_LITTLE_ENDIAN && CPU_32v7 > > Nothing in the patch series really explains this restriction, so it > should be in the commit message. Arnd mentions some atomics > etc, but we really need to know exactly why this is in the patch. This should probably work with armv6 targets, for v5 or v4 Targets a different target would have to be specified in the KBUILD_RUSTFLAGS. Rust also has some big endian arm targets. > > I'm a bit surprised by this since the rustc LLVM backend nowadays > support all old ARM ISAs. I would have expected: > > select HAVE_RUST if AEABI > > Ideally this should work on any ARM core, but it's fair to require > EABI. > > The big reason: I think we want to be able to use Rust in kernel > core components sooner than ARMv5 goes away from the kernel. > > If testing is the only issue, I can provide testing on ARMv4, v5, > ARMv5 BE etc, just tell me how to test. (But I guess it's more than > that...) The main reason that I only did this for ARMv7 was that I'm not very familiar with older arm versions and that I only have v7 hardware for testing. I currently don't have much time to work on this, but when/if it works in qemu I'll send you a message to test it on HW. Cheers Christian