This video shows Xen 3.5-unstable (changeset 20143), VT-d, pv-ops dom0 kernel 188.8.131.52, VGA passthrough, HD audio passthrough, and Windows XP HVM guest operating system in action.
Host Operating System Domain 0: Fedora 11 Linux x86-64 64-bit
Domain U: Windows XP Home Edition SP3 32-bit HVM Virtual Machine
Xen Hypervisor Version: 3.5-unstable changeset 20143
Paravirt-Operations Dom0 Kernel: 184.108.40.206 (Jeremy Fitzhardinge's git tree)
Intel GFX Passthrough Patches Applied: Version 1 (Provided by Han Weidong Intel)
Motherboard: Intel DQ45CB
BIOS Version: 0093
Processor: Intel Pentium Dual Core E6300
Graphics Card: nVidia GeForce 8400 GS PCI Express x16
Memory: 8GB DDR2-800
Version of Xen GPL PV (GPLPV) Drivers Installed: 07/15/2009 0.10.0.86
Full implementation details are here: http://lists.xensource.com/archives/html/xen-devel/2009-10/msg01134.html
VGA and HD audio passthrough are fully working. Although device manager reports that it is working, OHCI IEEE1394 firewire controller passthrough is not working as expected. Video cameras with firewire attached to the firewire port cannot be detected.
USB optical mouse and USB keyboard have also been successfully passed through to Windows XP HVM guest.