This procedure works with fully virtualized VMs. I would assume it works with paravirtualized VMs as well...
Shut down and power off your VM
Unplug and re-plug your USB device to see what it appears as in dmesg, then run
dmesg | grep ^usb
See these lines?:
usb 3-2: USB disconnect, address 7
usb 3-2: new low speed USB device using uhci_hcd and address 8
usb 3-2: configuration #1 chosen from 1 choice
This indicates that it is connected to Bus 003 as Device 008. Now run this:
Now look a device at Bus 003 Device 008:
Bus 003 Device 008: ID 04b9:0300 Rainbow Technologies, Inc.
Note the ID...
Open the config.sxp file for the domain, usually located at:
Look for a section similar to this:
Add your USB device:
Start your VM