Apparently it is much faster. Especially during savefile preparation -
tar reads the whole file, while bsdtar gets file map and reads only used
regions.
Define it only when really needed:
- during VM creation - to generate UUID
- just before VM startup
As a consequence we must handle possible exception when accessing
vm.libvirt_domain. It would be a good idea to make this field private in
the future. It isn't possible for now because block_* are external for
QubesVm class.
This hopefully fixes race condition when Qubes Manager tries to access
libvirt_domain (using some QubesVm.*) at the same time as other tool is
removing the domain. Additionally if Qubes Manage would loose that race, it could
define the domain again leaving some unused libvirt domain (blocking
that domain name for future use).
Provide vm.refresh(), which will force to reconnect do QubesDB daemon,
and also get new libvirt object (including new ID, if any). Use this
method whenever QubesDB call returns DisconnectedError exception. Also
raise that exception when someone is trying to talk to not running
QubesDB - instead of returning None.
Libvirt will replace domain XML when trying to define the new one with
the same name and UUID - this is exactly what we need. This fixes race
condition with other processes (especially Qubes Manager), which can try
to access that libvirt domain object at the same time.
It have nothing to do with xenstore, so change the name to not mislead.
Also get rid of unused "xid" parameter - we should use XID as little as
possible, because it is not a simple task to keep it current.
It is used by just started DispVM to notice when restore process
completed. Alternatively it could watch its own domid, but lets do it in
Xen-independent way.
When called from libvirt->libxl, there is libvirt lock taken on that
domain. Because of that, we can't access libvirt domain, so basically
any runtime information. Without that --offline-mode, script waited on
the lock and then was killed by libxl after a timeout - before actually
committing the changes.
Many functions and especially standalone tools takes the lock itself, so
to prevent deadlocks, as a rule execute the tests with lock released.
Also reload qubes.xml before cleanup.
The statement that unlock_db() is always called directly after save() is
no longer true - tests holds the lock all the time, doing multiple saves
in the middle.
