RHEL Support

Posted Sep 24, 2024 14:20 UTC (Tue) by jgg (subscriber, #55211)
Parent article: Committing to Rust in the kernel

> Gunthorpe said that he would like to see a clear message that Rust is a success before jumping into it; he also is unable to work with Rust until a suitable compiler is available in RHEL. Airlie said that perhaps, for Gunthorpe, the time had not yet come.

To clarify my remark, I was speaking from the perspective of our community members that are working on server/enterprise/hyperscale projects where deplyoment of the project usually requires running on some older kernel via backports. Using RHEL as some shorthand for this ecosystem. This is a distinctly different set of concerns from Fedora, Android or Embedded communities.

The issue here is not that a "suitable compiler" exists in RHEL, but that all the distros have enabled Rust in their kernels, that they fully support Rust on their commercially relavent server architectures (S390 and Power! I have users!) and everything is in place to backport and consume an add-on-top "driver backport package". There are many technical gaps still to be resolved here.

This was, in part, a reaction to Miguel's earlier remark that companies were reluctant to participate. It will be very hard for a company to fund writing new code in Rust if none of their customers can run that code and they have to write a C version anyhow.

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RHEL Support

Posted Sep 25, 2024 4:57 UTC (Wed) by admalledd (subscriber, #95347) [Link] (3 responses)

FWIW, in -theory- 360, POWER, Sparc, etc, should work with Rust. Just they aren't "Tier 1 officially supported" yet since they lack commercial backing/QA/validation, and getting them into the kernel would be its own minor project.

For clarity on ISA/Platform support: https://doc.rust-lang.org/nightly/rustc/platform-support....

Though the above is more about applications, not kernels, you can (mostly) just pay attention to the first bit of a platform-triple there for what ISA is supported. That page also clarifies better than I could what T1/T2/T3/etc all mean on "officially supported".

That is all for the LLVM backend, and there are of course the two projects (codegen-gccjit and GCC-rs) to use GCC in some flavor instead.

So yea, there is concern still on missing platforms vs the Linux Kernel, but the hope is the commercial interests involved with those will either (1) support LLVM to those, or (2) support one or the other GCC project.

All that said, still likely years away for any of the missing platforms to need to care about Rust: many of the subsystems and drivers likely to be written won't ever be intended for such legacy platforms anyways.

RHEL Support

Posted Sep 25, 2024 8:44 UTC (Wed) by farnz (subscriber, #17727) [Link] (2 responses)

As a really quick summary, only x86-32, x86-64 and AArch64 are in Tier 1. Tier 2 brings in AArch32, LoongArch, RISC-V, PowerPC, SPARC64 and WASM. Tier 3 then brings in AVR, C-SKY, MIPS, SPARC32, S390x (but not plain S390) and 68k.

Very roughly, the tiers are:

Tier 1 blocks merging of PRs if any builds or tests fail in CI.
Tier 2 blocks merging of PRs if any builds fail in CI; tests are allowed to fail.
Tier 3 simply has one or more people promising to work on fixes if it fails to build in CI.

RHEL Support

Posted Sep 25, 2024 10:28 UTC (Wed) by sam_c (subscriber, #139836) [Link]

What ends up being problematic for us is that only certain tiers get "host tools" built which means we have to build our own binaries for distributing Rust. sparc64 is an example.

RHEL Support

Posted Sep 26, 2024 12:29 UTC (Thu) by arnd (subscriber, #8866) [Link]

I also see hexagon and xtensa in the tier 3 list of the rustc manual, leaving only 7 architectures with no support at all, which are also the ones with very few users these days:

alpha, parisc and superh are old, with the latest CPU cores dating back to 2005, any work going on here is driven by hobbyists, but m68k shows that this may still happen.

arc, microblaze, and nios2 are still available for new designs but most users have moved on to risc-v here, and I don't expect anyone to put money into a rustc port. Nios2 and microblaze are likely to get phased out from the kernel in the next few years. Openrisc is somewhere between those, as a softcore that is not owned by a single company.