Re: Rust in Qemu BoF followup 2: Rust toolchain availability

[David Gibson]

On Thu, Sep 30, 2021 at 11:45:11AM +0100, Daniel P. Berrangé wrote:
> On Thu, Sep 30, 2021 at 11:59:42AM +1000, David Gibson wrote:
> > Hi again all,
> > 
> > I've now done.. or at least started... the second part of my followup
> > from the KVM Forum BoF on Rust in Qemu.
> > 
> > I've extended the page at https://wiki.qemu.org/RustInQemu with
> > information on Rust toolchain availability.  However, I found I had a
> > lot more open questions on this one, so there are quite a lot of gaps.
> > 
> > In particular:
> >  * I haven't so far figured out how to definitively check package
> >    information for RHEL & SLES (they're not covered by repology, and
> >    RHEL module structure confuses me, even as a RedHatter)
> 
> Don't worry about RHEL/SLES directly wrt repology.
> 
> For RHEL, just use corresponding CentOS as a proxy
> 
> For SLES, just use corresponding openSUSE version as a proxy

That makes sense, I've updated the table accordingly.

> >  * I'm not at all sure what criteria to use to consider something as
> >    having "good enough" rustup support, so that information is all
> >    blank so far
> >  * I've taken a bit of a stab in the dark about what Rust version is
> >    recent enough for our purposes (1.31.0).  I strongly suspect we're
> >    going to want to move that to something more recent, but I don't
> >    know what, which will mean revising a bunch of stuff
> 
> Our platform support matrix defines what distros we target.
> 
> IOW we would have a strong preference for a rust version that is present
> in those distros. Essentially tests/docker/dockerfiles/*.Dockerfile
> need to be able to pull in the rust packages from the distro, if
> we are to make it mandatory.

Works for me.  Let's definitely *not* be like Kata, which installs Go
& Rust from upstream binaries, and builds qemu & a guest kernel from
source in its CI runs.

> If rust is to be strictly optional, then we have way more flexibility
> in choosing the version. We do not need to cover all distros in the
> support matrixk *provided* the rust is only used for new functionality
> and we're not introducing it as a dependancy for existing functionality.

Right, but part of the point of this exercise is seeing if we can make
this mandatory, so that's the perspective I'm working from.

> ie existing features previously released must keep working across all
> distros in the matrix. new features from a release can set a higher
> bar, since by definition it can't regress existing usage.
> 
> 
> Regards,
> Daniel

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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