• find the usb device on the host machine

lsusb

Bus 002 Device 003: ID 1a56:dd01

• edit a xml file for attaching

cat attatch-usb.xml

<hostdev mode='subsystem' type='usb' managed='yes'>
  <source>
      <vendor id='0x1a56'/>
      <product id='0xdd01'/>
      <address bus='2' device='3'/>
  </source>
</hostdev>

• attach the usb into the virtual machine

virsh attach-device instance-00000460 /path/to/attach-usb.xml --persistent

• now you can find the usb device in the virtual machine named instance-00000460