While libvirt handle locking itself, there is also Qubes-specific
startup part. Especially starting qrexec-daemon and waiting until
qrexec-agent connect to it. When someone will attempt to start VM the
second time (or simply assume it's already running) - qrexec will not be
connected yet and the operation will fail. Solve the problem by wrapping
the whole vm.start() function with a lock, including a check if VM is
running and waiting for qrexec.
Also, do not throw exception if VM is already running.
This way, after a call to vm.start(), VM will be started with qrexec
connected - regardless of who really started it.
Note that, it will not solve the situation when someone check if VM is
running manually, like:
if not vm.is_running():
yield from vm.start()
Such code should be changed to simply:
yield from vm.start()
FixesQubesOS/qubes-issues#2001FixesQubesOS/qubes-issues#2666
018877a19c