Re: [RFC PATCH v1 0/6] Implement ARM PL011 in Rust

[Alex Bennée]

Stefan Hajnoczi <stefanha@gmail.com> writes:

> On Mon, 10 Jun 2024 at 16:27, Manos Pitsidianakis
> <manos.pitsidianakis@linaro.org> wrote:
>>
>> On Mon, 10 Jun 2024 22:59, Stefan Hajnoczi <stefanha@gmail.com> wrote:
<snip>
>> >>
>> >> 1. Tooling
>> >>    Mostly writing up the build-sys tooling to do so. Ideally we'd
>> >>    compile everything without cargo but rustc directly.
>> >
>> >Why would that be ideal?
>>
>> It remove the indirection level of meson<->cargo<->rustc. I don't have a
>> concrete idea on how to tackle this, but if cargo ends up not strictly
>> necessary, I don't see why we cannot use one build system.
>
> The convenience of being able to use cargo dependencies without
> special QEMU meson build system effort seems worth the overhead of
> meson<->cargo<->rustc to me. There is a blog post that explores using
> cargo crates using meson's wrap dependencies here, and it seems like
> extra work:
> https://coaxion.net/blog/2023/04/building-a-gstreamer-plugin-in-rust-with-meson-instead-of-cargo/
>
> It's possible to use just meson today, but I don't think it's
> practical when using cargo dependencies.

I did find the wrap approach very useful in giving a useful checkout
with --download that I can edit and tweak but is still integrated into
the build. This is helpful when working with very new libraries that
haven't been widely packaged yet. Distro's can choose or not choose to
use --download as they wish.

<snip>
>> >
>> >Do you mean vendoring by committing them to qemu.git or just the
>> >practice of running `cargo vendor` locally for users who decide they
>> >want to keep a copy of the dependencies?
>>
>>
>> Committing, with an option to opt-out. They are generally not big in
>> size. I am not of strong opinion on this one, I'm very open to
>> alternatives.

I think we generally host stuff we explicitly need in separate mirrors
or even a little light forking (testfloat does this).

> Fedora and Debian want Rust applications to use distro-packaged
> crates. No vendoring and no crates.io online access. It's a bit of a
> pain because Rust developers need to make sure their code works with
> whatever version of crates Fedora and Debian provide.
>
> The `cargo vendor` command makes it easy for anyone wishing to collect
> the required dependencies for offline builds (something I've used for
> CentOS builds where vendoring is allowed).
>
> I suggest not vendoring packages in qemu.git. Users can still run
> `cargo vendor` for easy offline builds.
>
<snip>

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro