[Pkg-xen-devel] Bug#1122188: xen-hypervisor-4.20-amd64: USB Passthrough to qemu HVM not pussible

[Maximilian Engelhardt]

On Monday, 8 December 2025 14:40:40 CET Volker Gruenewald wrote:
> [root at debian01:/usr/local/admin/scripts]# xl usbdev-attach smart10 hostbus=1
> hostaddr=5 libxl: error: libxl_qmp.c:1837:qmp_ev_parse_error_messages:
> Domain 13:Bus 'xenusb-0.0' not found libxl: error:
> libxl_device.c:1500:device_addrm_aocomplete: unable to add device
> libxl_device_usbdev_add failed.
> 
> USB Controlles is created as expcted, but not possible
> 
> [root at debian01:/usr/local/admin/scripts]# xl usb-lis smart10
> Devid  Type         BE  state usb-ver ports
> 0      devicemodel  0   0     2       6
>   Port 1:
>   Port 2:
>   Port 3:
>   Port 4:
>   Port 5:
>   Port 6:

This looks like you are trying to pass through a usb1 device, but there is 
only a virtual usb2 controller in your vm.

If you adjust your vm configuration to create a virtual usb1 controller this 
error will probably go away. You can do this by specifying

usb = 1

or alternatively for an usb1 and usb2 controller

usbctrl = [ "version=1, ports=2", "version=2, ports=6" ]

in your vms configuration.

However you likely will run into a different error:

$ xl usbdev-attach testvm hostbus=1 hostaddr=4
libxl: error: libxl_qmp.c:1837:qmp_ev_parse_error_messages: Domain 6:Parameter 'hostaddr' expects uint64
libxl: error: libxl_device.c:1500:device_addrm_aocomplete: unable to add device
libxl_device_usbdev_add failed.

This is a bug in xen and I'm currently in contact with xen upstream about 
that. A possible fix is here:
https://lore.kernel.org/xen-devel/20251215135124.11410-1-anthony@xenproject.org/