Re: mapping from debian arch to qemu arch

[Michael Tokarev <mjt@tls.msk.ru>]

13.02.2023 00:51, Christian Kastner пишет:
> Hi all,
>
> apologies for the late reply.
>
> On 2022-12-28 17:20, Johannes Schauer Marin Rodrigues wrote:
> > Quoting Michael Tokarev (2022-12-25 08:01:31)
> > > BTW, does sbuild really needs qemu-system (and sbuild-qemu to begin with)?
> >
> > sbuild-qemu uses the autopkgtest backend of sbuild to run builds with qemu
> > isolation. So for building packages, sbuild-qemu only uses qemu-system-XXX
> > indirectly via autopkgtest. The sbuild scripts that need qemu-system-XXX
> > directly are sbuild-qemu-update and sbuild-qemu-boot that assist with updating
> > or entering a qemu image for autopkgtest use, respectively.
>
> Correct, sbuild-qemu needs a mapping from Debian arch to QEMU arch so
> that when a user invokes
>
>      $ sbuild-qemu --arch ppc64el *.dsc
>
> sbuild-qemu knows which QEMU binary to request:
>     amd64     needs   qemu-system-x86_64
>     ppc64el   needs   qemu-system-ppc64le
>     arm64     needs   qemu-system-aarch64
>     etc.
>
> That's all there is.
>
> If there would be some system-wide solution for this (via symlinks or
> whatever), great!

Yesterday I uploaded a new qemu release (to experimental), with the
following commit:
https://salsa.debian.org/qemu-team/qemu/-/commit/09115a82cd1cef9f76fc36d5ca5676ed494554ea

which should fix this very issue.  You can now depend on, say,
qemu-system-arm64, or run qemu-system-amd64 binary.

Maybe next time I'll rearrange qemu-system-foo split somehow, but
the scheme will (hopefully) stay.

..
> > > For now, I'm not really sure we actually needs even the symlinks mentioned
> > > above. This is just due to my misunderstanding, I guess.  For example, the
> > > sbuild-qemu thing, - it needs not only the qemu-system-$arch binary naming
> > > but also the package naming, it seems.
> >
> > Ah you are referring to the Depends and Recomends of sbuild-qemu. Maybe this is
> > a mistake. I'm not maintaining sbuild-qemu but Christian Kastner is, so they
> > will be much more fit to answer all these questions. Putting them in CC. Maybe
> > sbuild-qemu should Depend on the qemu-system meta-package to automatically pull
> > in qemu-system-$foo for all possible architectures?
> Perhaps I'm misunderstanding something, but the current setup of
>
>     Depends: qemu-system-x86
>     Recommends: qemu-system-arm, qemu-system-ppc
>
> was chosen because those are the architectures supported by autopkgtest,
> and thus by sbuild-qemu. There needs to be at least one qemu-system-* to
> be useful, and x86 is the dominating arch.
>
> But I'm totally open to adapting this in any way that might be more
> convenient to you.

I don't really know what to put there. Maybe qemu-system-amd64 (as of now),
and maybe any qemu-system-foo, probably with an alternative.  I guess I can
provide qemu-system-any in all qemu-system-foo packages, so the above will
look like:

  Depends: qemu-system-amd64 | qemu-system-any.

Dunno really.  For now, I'm not yet sure how to re-split the thing better,
so let's keep it the way it is now :)

Thanks,

/mjt