Re: [RFC 00/18] rust: split qemu-api

["Marc-André Lureau" <marcandre.lureau@redhat.com>]

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Hi

On Tue, Aug 26, 2025 at 6:44 PM Paolo Bonzini <pbonzini@redhat.com> wrote:

> On 8/26/25 16:04, marcandre.lureau@redhat.com wrote:
> > From: Marc-André Lureau <marcandre.lureau@redhat.com>
> >
> > Hi,
> >
> > qemu-api is providing bindings for various internal libraries. Instead,
> the
> > bindings requirements should match the various libraries and use the
> minimal set
> > of dependencies.
> >
> > An initial Rust-only "common" crate is introduced, then "util" (for
> libqemuutil,
> > without bql), "migration" (so it doesn't depend on bql), "bql", "qom"
> (arguably,
> > bql shouldn't be required?), and "chardev", "system", "hwcore". Finally
> the
> > qemu-api crates are renamed and repurposed.
> >
> > This involves a lot of code churn, so hopefully it can be reviewed and
> merged
> > early and iterated upon :)
>
> The one comment that I would like to handle before merging, is that I'd
> prefer to keep the preludes and, in fact, even add more exports to them
> since they can now be chosen per-crate.  Ideally, many of the crates
> you've crated would be accessed through many "use xyz::prelude::*"
> statements.
>

It's not very useful if you have to include all the preludes though :)

Also, prelude feels a bit too much magic and may pollute namespace. In
general, not so many crates provide them and that's usually a good thing
imho, since you can explicitly import what you need, and LSP and good error
report make that fairly trivial.

So, I am not convinced having each crate its own prelude is a good thing,
but I don't care much. Can easily be added back though.


>
> Also, if I understood correctly the split util/errno.rs can move to
> common/.  While it has a dependency on libc, it doesn't need bindgen.
>
>
True, I will move it


> There's a bunch of code duplication for the various bindings.rs and
> build.rs files, which is not ideal but shouldn't grow much more than
> this.  I wonder if, later, common code across build.rs could be written
> just once by adding a new crate (e.g. "qemu_meson") to the workspace,
> that can be used as a build-dependency.
>
>
I am not sure, but I can try. Alternatively, we can have a build.rs
symlink, if we can guess the module path.

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