Further to my last post, I have removed the xen-pciback module from the Dom0 kernel, and reloaded it as modprobe xen-pciback passthrough=1 I now have the PCI device on the DomU matching the Dom0 Device usb usb1: SerialNumber: 0000:00:1a.0 instead of 0000:00:00.0 However I now have this error ehci_hcd 0000:00:1a.0: Unlink after no-IRQ? Controller is probably using the wrong IRQ. does this give a clue as to what is going on? Many thanks Francis -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.centos.org/pipermail/centos-virt/attachments/20160703/0afd0fe3/attachment-0004.html>