Re: qemu-kvm-0.13.0, 2.6.37.1 - after migration, some of guests got stuck

Philipp Hahn
2011-02-21T07:44:06Z

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Hello,

I'm no KVM core developer, so please take my advise with a grain of caution.

Am Sonntag 20 Februar 2011 20:32:35 schrieb Nikola Ciprich:
> I've just migrated a bunch of guests from one node to another
> due to upgrading host kernel from 2.6.37 to 2.6.37.1.
> After that, some of guests started consuming 100% of CPU time and their os
> seems to be stuck.
>
> Looks like all the stuck guest were running 2.6.32 with kvm paravirt
> enabled. others running same as well as different kernels seem to be ok,
> including windows guests.

I also sometimes experience problems with migrated (in my case: suspended)
VMs, see <http://marc.info/?l=kvm&m=129484437222822&w=2>: They were either
stuck in an interrupt storm or did not receive any interrupts any more (looks
like some interrupts relates state gets not saved/restored properly).
For me the following did help:
1. Suspend VM to disk
2. Restart VM with the -no-kvm-irqchip Option
Perhaps you could test that as well. (An alternative would be to use qemus
internal debugger or gdb to remote debug the VM and detect what your VMs are
doing, especially "x/20i $rip" to dump the next 20 assembler instructions)
Please be advised, that -no-kvm-irqchip opens a new can of worms and should
only be used to diagnose the problem. You probably should also backup the
save file and use the -snapshot option to be able to repeatly test different
strategies.

Sincerely
Philipp
--
Philipp Hahn Open Source Software Engineer hahn@univention.de
Univention GmbH Linux for Your Business fon: +49 421 22 232- 0
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