- A Devices section of each host lists its PCI devices by IOMMU group and
its USB devices: what each is (vendor, product, IDs, class, driver), what
the host itself has on it (its network interfaces, disks and graphics
card, anywhere below it) and the VMs whose definitions name it.
- A VM names a PCI device by its address, a USB device by its address or
by its model only; a VM that names a model only is shown on every device
of that model, which one it takes is known only when it starts.
- A host without IOMMU groups says that no PCI device can be given to a VM
and how to turn the IOMMU on.
- One listing of the host's node devices, one XML read each (a device gone
meanwhile is left out), and the VMs' definitions read once; nothing is
shown when they cannot be read, as a device would look free.
- Read only: giving devices to VMs comes in the next layers.
