usb-controller-qemu-xhci-limit.xml

<domain type='qemu'>
  <name>QEMUGuest1</name>
  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
  <memory unit='KiB'>219136</memory>
  <vcpu placement='static'>1</vcpu>
  <os>
    <type arch='x86_64' machine='pc'>hvm</type>
  </os>
  <devices>
    <emulator>/usr/bin/qemu-system-x86_64</emulator>
    <controller type='usb' index='0' model='qemu-xhci' ports='16'/>
    <memballoon model='none'/>
  </devices>
</domain>