[libvirt] libvirt starts KVM domain without -enable-kvm

[Reinier Schoof]

Hey,

we're running a VM-pool based on libvirt and QEMU/KVM. The host machines 
run debian 6 (squeeze). All VM's have a similar libvirt XML-definition. 
Since we've moved to the combination of Linux kernel 3.2.0-1 and libvirt 
0.9.9 (installed from testing/wheezy repo's), we periodically notice 
poor performance of new(ly started) VM's and after inspection they turn 
out to be started without the qemu option -enable-kvm. In 
/var/log/libvirt/qemu/$VM-name.log a line like this is shown:

20529: error : qemuBuildCommandLine:3681 : unsupported configuration: 
the QEMU binary /usr/bin/kvm does not support kvm

After a virsh destroy/start, using the same XML-definition, the VM is 
started WITH -enable-kvm. Looking at the libvirt source of 0.9.9, I 
can't imagine this being the result of a race condition or other strange 
circumstance: it simply parse 'qemu -help', which always give exactly 
the same output.

I've tried reproducing the problem by continuously destroy, undefine, 
define and start the same VM and then grepping the kvm-commandline for 
the absence of -enable-kvm, without any result.

The XML-definition includes
	<domain type='kvm'>
and
	<emulator>/usr/bin/kvm</emulator>

Does anyone recognize this behaviour of libvirt?

Thanks,
Reinier Schoof

# virsh version
Compiled against library: libvir 0.9.9
Using library: libvir 0.9.9
Using API: QEMU 0.9.9
Running hypervisor: QEMU 0.15.0
Linux 3.2.0-1-amd64 #1 SMP Fri Feb 17 05:17:36 UTC 2012 x86_64 GNU/Linux


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