Re: [libvirt] [PATCH] domain: don't try to interpret <driver> as virtio config for hostdev interfaces

This resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1046337 The <driver> type attribute of an interface is interpreted in two different ways depending on the <interface> type - if the interface is type='hostdev', then the driver name describes which backend to use for the hostdev device assignment (vfio or kvm), but if the interface is any emulated type *and* the model type is "virtio", then the driver name can be "vhost" or "qemu", telling which backend qemu should use to communicate with the emulated device.

This isn't noticed until the next time libvirtd is restarted - as it is reading the status of all domains, it encounters the above interface definition, logs an error: internal error: Unknown interface <driver name='vfio'> has been specified and fails to reload the domain status, so the domain is marked as inactive.

The solution is to stop the parser from interpreting <driver> attributes as if the device was an emulated virtio device, when it is actually a hostdev. (Although the bug has existed since vfio support was added, it has just recently become more apparent because libvirt previously didn't automatically set the driver name for hostdev interfaces in the domain status to vfio/kvm as it does since commit f094aa, first appearing in v1.1.4.)