My Fedora 19 got an update for KVM. It was a no biggie, nothing really happened at the time.
Then one of the virtual guests got a new kernel (RHSA-2013:0911-1). I rebooted the guest and BANG! My KVM hung the entires machine. I have the Magic SysRq enabled, but nothing. The box was completely hung.
The "funny" part happened after I forced a reboot from the button. The box wouldn't boot! My LDAP was corrupted. All I got was a "BDB0060 PANIC: fatal region error detected; run recovery" -message.
There is the /usr/bin/db_recover -tool, but it just said FUBAR. I didn't get the actual phrase, but surely you'll get the meaning. Then, what next? I was lucky enough to have a 3 week old slapcat of my entire LDAP. That was plenty of luck for me. But the morale of the story is, that I'll need to start dumping the LDAP or change the back-end format into something more recoverable.