[Qemu-devel] Question about how to distinguish a usb device in usb pass-through feature

[Yuanjing (D)]

Hi,

I want to provide feature that  pass-through host’s usb device to guest os in  Openstack.

I have question about how to distinguish a usb device.

 

I have read some introductions and made some tests. I think qemu supports two ways to identify a host usb device:

(1)host:bus.addr

(2)host:vendor_id:product_id

I think they both have restriction on some use cases:

(1) ‘host:bus.addr’ is not appropriate if more than one usb devices with the same ‘host:bus.addr’ in a host.

(2) The addr(device number) may change every time unplug/plug usb device of a host.  One this happen the guest may reboot failed with wrong host:bus.addr.

 

I noticed that Vmware supports technology ‘autoconnection’, they pass-through usb device by using usb path of the device on the host(physical topology and port location).

Once unplug usb device and plug usb device again with the same usb path, the new device appears and is connected to the guest.

 

I am not a qemu/system programmer  and I apologize if I am missing something very obvious.

Hope somebody can help me to find the best way to distinguish a usb device?

 

Thanks in advance