[Solved] KVM guests occassionally hang :S

[rauar]

Hi, couldn't find any related topics. So here goes the problem:

I've 5 Linux (Ubuntu 9.04) guests running on KVM and managed by libvirtd. However since a while (really not sure since when but I would say 3-4 months) the guests sporadically fail to start when booting the host. It's hard to get them all up and running properly. Failing here means: most of them are not reachable via ssh nor pingable - no DHCP requests coming from the guests as well.

"virsh list" hangs on output (showing none of the guests or sometimes 1-2 of them and then hangs in between the list of guests). Stopping the guests hangs as well - most often like that a hard reset is necessary. Even the terminal on the host where the virsh commands are executed starts hanging but returns after a while.

If I would have to guess I'd say it's somewhere a bug in between the kernel moduls and libvirt. Qemu logs show no errors except the used command to start the guest and IN/OUT records when stopping the guest.

Installed versions:

app-emulation/kvm-kmod-2.6.34.1
app-emulation/libvirt-0.8.2-r1
app-emulation/qemu-kvm-0.12.5
sys-kernel/vanilla-sources-2.6.30.9
sys-kernel/vanilla-sources-2.6.32.9
sys-kernel/vanilla-sources-2.6.34

Linux athene 2.6.34 #3 SMP Sun Jul 18 00:12:52 CEST 2010 i686 Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz GenuineIntel GNU/Linux

I tried to delete all interface tags in the libvirt guest config so that they get recreated to make sure it's not a problem with a broken config due to the age of the guests (2 years round about). Reduced the autostart to one single VM and even this single guest hangs 50% of the restarts or even more.

Anyone with the same experiences with this combo ? The stuff was running rock-solid a while ago.

Regards, Alex

[rauar]

Libvirt's saving of the VM state caused the problems. Saved VM dumps couldn't be loaded again (causing the hangs).

Disabled it and properly shutting down the VMs now (check /etc/conf.d/libvirtd). This was the original behavior somewhen in the past anyway. Rock-solid and lightning fast VMs now again.

Alex