Вставил флешку. Создал для нее xml:
<hostdev mode='subsystem' type='usb' managed ='yes'>
<source>
<vendor id='0x058f'/>
<product id='0x6387'/>
</source>
</hostdev>
virsh attach-device vm usb.xml
virsh dumpxml vm > temp.xml
virsh define temp.xml
virsh edit vm
<hostdev mode='subsystem' type='usb' managed ='yes'>
<source>
<vendor id='0x058f'/>
<product id='0x6387'/>
<address bus='1' device='15'/>
</source>
</hostdev>