This Week in Spectrum, 2025-W29

Alyssa Ross
2025-07-21T07:42:00Z

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The main thing that's been happening this week is a lot of back and
forth between Demi and me on PipeWire in VMs. The series is now in its
fifth iteration[1], and is shaping up well. I'm happy that we're
discussing it on the list so much, because it will make it easy to refer
back to in future for context of why decisions were made.

For my part, I've been mostly trying to find solutions to problems Demi
has been encountering as she gets set up to work on Spectrum. To that
end, I fixed a couple of build issues that occurred when KVM wasn't
available[2][3], removed the need to remember to run "make clean" after
modifying the list of installed packages to avoid ending up with a
broken build[4], and spent some time trying to debug why QEMU's
virtio-gpu implementation doesn't seem to work nearly as well as
crosvm's, despite them being built on the same code. (I haven't made
much progress with the latter though — I have a gut feeling it's a
memory safety problem, but running Valgrind on QEMU has so far been
painful.) I also figured out and fixed the Cloud Hypervisor bug[5] I
mentioned last week, so once we update Cloud Hypervisor, the file
chooser portal no longer intermittently fails to configure itself, and I
did the usual server updates and Nixpkgs maintenance.

Yureka has been making progress with forwarding packets out of a network
driver VM to host userspace, where we plan to do routing with the aim to
later move it into a VM as well. She's also started working on
implementing a vhost-user backend, which is how the host userspace
router will get packets to and from the application VMs. Sounds like
it's still very much in the experimental phase, so there's no public
code to link to for any of this as yet.

[1]: https://spectrum-os.org/lists/archives/spectrum-devel/a7325ee5-eb7f-458c-9be6-404db676dd81@gmail.com/
[2]: https://spectrum-os.org/git/spectrum/commit/?id=1b33fcabdad8e4b76587848ad294bc056ca997f1
[3]: https://spectrum-os.org/git/spectrum/commit/?id=89b80752a275a4ca1818a49d86f27cca9e323389
[4]: https://spectrum-os.org/git/spectrum/commit/?id=c1e1449b2173913f08828bafc62dc112b2534acc
[5]: https://github.com/cloud-hypervisor/cloud-hypervisor/commit/ec8fceb4a6a537c4d838287d47edc2c156379b4e

Until next week! I'll be at BornHack until Wednesday morning, so if you
are too and want to talk about Spectrum, get in touch. :)