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Mon, 2 Mar 2026 13:28:55 +0100 (CET) Message-ID: Date: Mon, 2 Mar 2026 13:28:50 +0100 X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V6 2/3] rust: Add PowerPC support To: Alice Ryhl , Mukesh Kumar Chaurasiya Cc: Miguel Ojeda , Link Mauve , ojeda@kernel.org, boqun.feng@gmail.com, gary@garyguo.net, bjorn3_gh@protonmail.com, lossin@kernel.org, a.hindborg@kernel.org, tmgross@umich.edu, dakr@kernel.org, corbet@lwn.net, maddy@linux.ibm.com, mpe@ellerman.id.au, npiggin@gmail.com, chleroy@kernel.org, peterz@infradead.org, jpoimboe@kernel.org, jbaron@akamai.com, rostedt@goodmis.org, ardb@kernel.org, rust-for-linux@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Jubilee Young , Matthew Maurer , David Wood , Wesley Wiser References: <20260210090023.2587534-1-mkchauras@gmail.com> <20260210090023.2587534-3-mkchauras@gmail.com> <0a176f95-eeba-428e-b19b-b08503d9ca5d@ralfj.de> From: Ralf Jung Content-Language: en-US, de-DE In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 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: >> On Tue, Feb 24, 2026 at 09:58:10AM +0100, Ralf Jung wrote: >>> Hi all, >>> >>> On 23.02.26 16:31, Miguel Ojeda wrote: >>>> On Mon, Feb 23, 2026 at 3:26 AM Mukesh Kumar Chaurasiya >>>> wrote: >>>>> >>>>> 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 . Kind regards, Ralf