from QEMU to libvirt(virsh) - add USB-port

Question

I would like to have following line translated from qemu optiones into libvirt xml.

-qemu-system-x86_64
-...
-usb -device usb-host,bus=usb-bus.0,hostbus=<bus>,hostport=<port> 

This adds a physical usb plug to a virtual machine. Most examples are shown and well documented for usb-bus/deviceID, not for this solution.

Edit: The tool virsh domxml-from-native qemu-argv MyArgV.sh has the following solution:

<qemu:commandline>
  <qemu:arg value='-device'/>
  <qemu:arg value='usb-host,bus=usb-bus.0,hostbus=1,hostport=10'/>
</qemu:commandline>

But this is not really what I wanted, because it is bypassing the libvirt system. So if the native tool can't find any solution, is there a general libvirt solution for passing USB-Ports?

I've also tried the virt-manager GUI for adding a USB-Port, but I was not able to find any possebilety to do so.

Is there maybe a possebilety to make a snapshot of a running qemu machine and replicate it with libvirt on the fly?

I found this webpage. But this one is describing how to assemble the usb-port hierarchy in the VM, not forwarding a host port to vm.

Answer 1

Unfortunately it isn't documented, but you can assign a USB device based on bus + device number with this syntax:

<hostdev mode='subsystem' type='usb' managed='no'>
  <source>
    <address bus='1' device='NNN'/>
  </source>
</hostdev>

unfortunately the device number here is the /dev/usb/bus/NNN number which changes every time you plug it in. There's not yet any support for picking the device based on hostport which is stable.

Answer 2

You can also find out the vendor and product ids from your USB device (by using lsusb) and then use this information to attach your USB device to your KVM:

$ lsusb
...
Bus 002 Device 018: ID 03f0:4217 Hewlett-Packard EWS CM1015
...

<hostdev mode='subsystem' type='usb'>
  <source>
    <vendor id='0x03f0'/>
    <product id='0x4217'/>
  </source>
</hostdev>

Found on https://rolandtapken.de/blog/2011-04/how-auto-hotplug-usb-devices-libvirt-vms-update-1.

However this will not work if you have more than one of such USB devices connected to the host.