Beside rpi3 usb emulation not being there you are using the wrong argument. bus= specifies the *guest* bus. hostbus= can be used to specify the host bus number. When passing through devices using vendorid and productid this should not be needed though. Oh, and you can't pass through usb hubs, only individual devices.
Beside rpi3 usb emulation not being there you are using the wrong argument. bus= specifies the *guest* bus. hostbus= can be used to specify the host bus number. When passing through devices using vendorid and productid this should not be needed though. Oh, and you can't pass through usb hubs, only individual devices.