Re: [libvirt] RFC: remove qemu commandline parsing?

qemu/qemu_parse_command.c powers 'sudo virsh domxml-from-native qemu-argv', parsing a qemu command line and attempting to turn it into libvirt domain XML. Some history: RFE: https://www.redhat.com/archives/libvir-list/2009-April/msg00266.html Patches: https://www.redhat.com/archives/libvir-list/2009-May/msg00321.html danpb blog post about related qemu-attach: https://www.berrange.com/posts/2011/07/13/attaching-libvirt-to-an-externa... At the time it was added, the parser was pretty comprehensive WRT to what libvirt XML features were available at the time. However it's quite hopelessly out of date these days and has been for a long time. As an example, the only -device it knows to parse is virtio-balloon, and it doesn't know anything about -netdev. So the parser can really only handle typical old style qemu options.

AFAICT The original motivation for adding this and qemu-attach was providing a more straightforward path for direct qemu users to switch to libvirt. Googling does provide some cases of users successfully converting very simple qemu invocations to libvirt XML. But at least from my experience I don't think these features every really moved the needle in this respect. If anything, it's been that managing qemu has only grown more complex over time, which has made libvirt and tools that use it all the more compelling over launching your own qemu command line (for end users, think manually setting up usb2 with qemu directly). But IMO all that is kind of beside the point. I don't think it's debatable that the code is largely unused, and it hasn't seen many material improvements in the last 5 years, with zero plans to improve it on the horizon. It's 2000+ lines of text processing code living in every libvirtd instance. Deleting it all and making the qemu_driver.c APIs just return errors seems like an easy win

considering we are trying to make libvirtd more modular and have a smaller footprint to facilitate usecases like kubevirt Thoughts?