In order to assign a whole PCI/e device to a VM one should use qvm-pci tool. E.g.

lspci

Find the BDF address of the device you want to assign, and then:

qvm-pci -a <bdf> <vmname>

E.g. assuming 00:1a.0 is a BDF of the device I want to assign to "personal" domain:

qvm-pci -a 00:1a.0 personal

Note that one can only assign full PCI or PCI Express devices. This means one cannot assign single USB devices -- only the whole USB controller with whatever USB devices connected to it. This limit is imposed by PC and VT-d architecture.