Start GUI session in VM before GUI daemon connects

[ben-grande]

The problem you're addressing (if any)

When preloading disposables on boot, they can be paused before the user unlocks their GUI session via the display manager / lock screen, but qubes that have this behavior, won't be able to open applications after the GUI session has started.

Test case:

1. Reboot QubesOS
2. Unlock LUKS
3. Do not unlock via the lock screen, instead use the Linux terminal with Alt-F2:
4. On the Linux terminal, choose a qube to do the following, such as personal:
   1. qvm-start personal
   2. qvm-run -p --no-gui personal -- systemctl --user --wait is-system-running
   3. qvm-pause personal
5. Still on the linux terminal, choose another qube to be in the control group and start it, such as work:
   1. qvm-start work
6. Switch back to the main display and login via the lock screen
7. Try to run a GUI application in the qube: qvm-run personal xterm (it will hang)

The difference I noticed is compared to qubes that are not paused when GUI session starts is that qubes-gui-agent on the domU does not connect to the socket once it is unpaused.

Restarting qubes-gui-agent on the domU has no effect.

To debug:

qvm-run -p --no-gui personal -- journalctl -xeu qubes-gui-agent
qvm-run -p --no-gui work -- journalctl -xeu qubes-gui-agent

Will notice that personal does not connect to the socket while work does.

Would help solve:

• Preloaded disposables #1512

The solution you'd like

Make qubes-guid retry the connection once a qube is unpaused.

The value to a user and who that user might be

Users of preloaded disposables would have their preloads as soon as possible instead of having to wait for a login via GUI, which may not be available on headless machines.

Completion criteria checklist

No response

List of found side effects

• notification proxy starts before GUI session in dom0 and fails - attempted solution: Wait for GUI session on the server side qubes-notification-proxy#13
• sys-gui doesn't work without dynamic resolution change, solution: Fix (partially) setting resolution on sys-gui qubes-gui-agent-linux#253
• input proxy doesn't retry (policy prompts) after user logs in: Delay connecting with gui-daemon until after starting Xorg qubes-gui-agent-linux#251 (comment)

[marmarek]

Make GUI daemon keep retrying connection if qube is paused

That isn't the problem, that is proposed solution, which IMO isn't necessarily the best one. Alternative could be for example qvm-start-daemon tool (the thing that starts GUI daemon) checking for the paused state and in that case delays gui-daemon startup until unpause event.

[marmarek]

And BTW none of those solutions are particularly nice for preloaded dispvms (started before user logs in). All of them have user session started only on dispvm use, which reduces benefits the preloading (just a bit, but still). For preloaded dispvms it would be better if gui-agent wouldn't need to wait for gui-daemon, but that's another topic.

[ben-grande]

The PR doesn't handle connections to paused qubes, it just create a distinction of preloaded qubes and only start the GUI session for them after the qube is marked as used.