On a vShpere server I'm trying to add a USB device (a USB HDD) to a guest. I have marked all USB controllers on the host for passthrough and have rebooted the host. I have added the EHCI+UHCI controller to the guest and have the guest powered on. When I try to add the device to the guest the Add Hardware wizard shows "USB Device (unavailable)" and when I select it I see "There are no USB devices available on the host."
How can I diagnose what's going on here? I think I've followed the proper steps to configure USB passthrough but I just can't seem to get it working.
Hardware:
HP ProLiant DL380 G7
Intel 5520 Chipset
Intel I/O Controller Hub 10 (82801JI)