RISC-V platform support?

[ifsheldon]

Summary

As now RISC-V MCUs, dev boards and even servers get more and more popular, I'd really like to see uv support for RISC-V Linux platforms. There're officially supported RISC-V cpythons, so I think at least pure Python packages run fine on RISC-V machines. I think rustc can happily compile uv on RISC-V machines, but I don't know if there's anything else to get to the minimum support.

Example

No response

[zanieb]

I'm generally supportive of this. We added RISC-V builds to python-build-standalone. The first step is presumably a cross-build of uv in our release workflow.

[FishAlchemist]

Current Rust Platform Support for RISC-V Linux

Tier 2 with Host Tools

target	notes
riscv64gc-unknown-linux-gnu	RISC-V Linux (kernel 4.20, glibc 2.29)
riscv64gc-unknown-linux-musl	RISC-V Linux (kernel 4.20, musl 1.2.3)

Tier 3

target	notes
riscv32gc-unknown-linux-gnu	RISC-V Linux (kernel 5.4, glibc 2.33)
riscv32gc-unknown-linux-musl	RISC-V Linux (kernel 5.4, musl 1.2.3 + RISCV32 support patches)

Ref: https://doc.rust-lang.org/1.84.0/rustc/platform-support.html
Ref: https://doc.rust-lang.org/nightly/rustc/platform-support.html

[konstin]

We already support risc-v for installing packages (#8934). For platforms without prebuilt binaries such as risc-v, you can install uv with cargo install --git https://github.com/astral-sh/uv uv. Please report anything that doesn't work on risc-v!

[ifsheldon]

@konstin Thanks for the information. I didn't find it as I didn't search for PRs. cargo install works flawlessly, but I cannot install Python with uv.

So, I guess I should make a feature request in https://github.com/astral-sh/python-build-standalone ? I don't know how hard it will be to build Python against, say, linux-riscv64gc-musl target, which should enable installing Python with uv.

[zanieb]

The downloads use the riscv64 tag without the gc variant. I'll need to look into the differences to see what's appropriate.

[zanieb]

The difference is that riscv64gc has the extra features needed to run Linux. (ie Mutiplication, Floats, Atomics, Fences and CSRs), as well as Compressed instructions (16-bit encodings).

rust-lang/rust-bindgen#2136

A little more detail; RISC-V is a modular ISA, meaning that it only has a mandatory base, and everything else is an extension. RV64GC is basically "RISC-V 64-bit, extensions G and C", with the G extension being a shorthand for some other extensions;

flatpak/flatpak#4594

Seems like we should change our builds to use the extended name? We'll discuss that upstream in astral-sh/python-build-standalone#504

[ifsheldon]

the G extension being a shorthand for some other extensions

Yes, and I remember G actually means "general" in the sense of general computing.

We could probably follow Rust Platform Support, like supporting riscv64gc-unknown-linux-gnu and riscv64gc-unknown-linux-musl, since Tier 2 supported targets of Rust means there's meaningful amount of user interest so they are "guaranteed to build" while Tier 3 targets are supported with basically best efforts.

[ifsheldon]

@zanieb Thanks!

I saw your commit 98e7cd0, so maybe you can add one more entry for building risc64gc-unknown-linux-musl target as well?

[zanieb]

Didn't mean to close this :)