[libvirt-users] usb post passthough stopped workng after kernel upgrade

[daggs]

Greetings,

I have a vm on debian 9.5 to which I pass an specific usb from the host. here is the relevant part in the vm's xml file:
    <hostdev mode='subsystem' type='usb' managed='yes'>
      <source>
        <vendor id='0x148f'/>
        <product id='0x5572'/>
      </source>
      <address type='usb' bus='0' port='1'/>
    </hostdev>
the address line was added automatically by libvirt.
everything was working well with kernel 4.15.11-1~bpo9+1 until I needed to upgrade the kernel to latest possible version due to usb issues
I've upgraded to 4.18.6-1~bpo9+1. after the upgrade, my vm doesn't starts anymore, I see this msg:
error: Failed to start domain router
error: internal error: qemu unexpectedly closed the monitor: 2018-11-02T13:43:32.174730Z qemu-system-x86_64: -device usb-host,hostbus=1,hostaddr=4,id=hostdev4,bus=usb.0,port=1: failed to find host usb device 1:4

how can a kernel upgrade cause this? is there a fix for this issue?

Thanks,

Dagg.