VirtualBox 5.1.2 intermittently fails to start or resume VMs

[rrendec]

I have recently upgraded to VirtualBox 5.1.2 (from VirtualBox 5.0.x) on my Fedora 24 host. After the upgrade sometimes machines fail to start or resume. I always start the machines from the GUI (i.e. not in headless mode). The behaviour is always the same and does not seem to depend on the guest OS (I tried multiple Linux versions and also Windows):

• The machine window opens. For fresh start VM it's black (i.e. I don't get to the point where I see the VirtualBox "bios" image), for resumed VMs it shows the last "screenshot" of the VM but greyed out.
• Start progress indicator is stuck at 0%, nothing happens.
• There is no CPU load or disk activity in the host OS.

I cannot close the VM window, the only way to get rid of it is killing the corresponding VirtualBox process.

Note that the same VMs sometimes start and sometimes don't. I haven't been able to figure out what influences that. Therefore I don't know a consistent method to trigger/reproduce this problem.

I'm attaching two logs for the same VM: VBox.log corresponds to a successful start-up. VBox.log.1 corresponds to one of these "frozen" start-ups.

[socratis]

Nothing out of the ordinary from your logs. This is where the logs start differ:

00:00:01.198092 NAT: Adding domain name localdomain
00:00:01.198097 NAT: DNS#0: 192.168.1.1
00:00:01.198486 Audio: Initializing PulseAudio driver
00:00:01.211790 Audio: Initializing VRDE driver
00:00:01.211866 AC97: Reset              <--- This is where the failed one stops
00:00:01.221537 VUSB: Attached 'HidMouse' to port 1
00:00:01.221655 PGM: The CPU physical address width is 36 bits
00:00:01.221663 PGM: PGMR3InitFinalize: 4 MB PSE mask 0000000fffffffff

So, it could be either failing at the sound initialization or at the point where the mouse is attached. Or it could be somewhere later and simply the log didn't register the events.

Can you disable the sound on your VM and see if anything changes? 5.1.2 has had its share with audio problems, so this maybe it. Give it a shot...

[rrendec]

Thanks for looking into the problem and for the feedback! I have switched back to VirtualBox 5.1.2 and disabled audio in the virtual machines like you suggested.

So far, the success rate is 100%, but since the problem doesn't always occur, I cannot tell if it's really solved. I will keep testing for a while and, if it doesn't happen again, I will assume it was indeed related to sound. In any case, I will post the results.