On a recent kvm upgrade to centos 6.3 I came across this error
virsh start linux6244
error: Failed to start domain linux6244
error: unsupported configuration: virtio only support device address type ‘PCI’
The error was from the virtio / disk section. The XML file had
<disk type='block' device='disk'>
<driver name='qemu' type='raw' cache='none'/>
<target dev='vda' bus='virtio'/>
<address type='drive' controller='0' bus='0' target='0' unit='0'/>
to fix the error the address type needed to be removed – specifically <address type=’drive’ controller=’0′ bus=’0′ target=’0′ unit=’0’/>
Once removed the vm started up with out problems.
On a test of a centos 6.2 system I removed theline and redefined the XML. On the redefine the line gets added again. It appears centos 6.2 requires the address type for virtio disks, but centos 6.3 actually fails with it.