Dynamic audiovm switching

[marmarek]

How to file a helpful issue

The problem you're addressing (if any)

Currently, changing audiovm requires target qube restart in practice. Technically, it is possible to change it without qube restart, if you know which services to restart in what order etc, but that's very much not obvious. This also includes the case of restarting said audiovm.

The solution you'd like

Changing audiovm at runtime should be seamless, as is changing netvm.

The value to a user, and who that user might be

Easier to use non-dom0 audiovm, mostly relevant for USB audio devices. Related to #7750, #8093.

Details

Implementation-wise, this requires:

• dom0 changing relevant qubesdb (or else) entry when audiovm is changed or (re)started
• pulseaudio agent watching said qubesdb entry and re-establishing vchan connection when needed
• pipewire agent doing the same
• stubdomain (currently also pulseaudio) agent doing the same - a caveat here, currently stubdomain doesn't have qubesdb at all (and has hardcoded domid=0 as audiovm), but it does have qrexec-agent