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This resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1046337 The <driver> name 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. The problem comes when someone has defined a an interface like this (which is accepted by the parser as long as no <driver name='xxx'/> is specified): <interface type='hostdev'> ... <model type='virtio'/> ... </interface> As libvirt storing this definition in the domain's status, the driver name is automatically filled in with the backend that was automatically decided by libvirt, so it stores this in the status: <interface type='hostdev'> ... <driver name='vfio'/> ... <model type='virtio'/> ... </interface> 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.)
LibVirt : simple API for virtualization Libvirt is a C toolkit to interact with the virtualization capabilities of recent versions of Linux (and other OSes). It is free software available under the GNU Lesser General Public License. Virtualization of the Linux Operating System means the ability to run multiple instances of Operating Systems concurrently on a single hardware system where the basic resources are driven by a Linux instance. The library aim at providing long term stable C API initially for the Xen paravirtualization but should be able to integrate other virtualization mechanisms if needed. Daniel Veillard <veillard@redhat.com>