Xen 4.0 is supposed to be able to use Citrix’s WHQL certified Windows paravirtualization drivers. Their advantage over the GPLPV drivers is that they are code-signed, meaning they run on 64-bit Windows without disabling some of Windows’ security features.
UPDATE 2011-10-17: Signed GPLPV drivers are now available. I have not yet tested them, but I assume the fix below is no longer necessary.
If you install the XCP drivers, make that registry tweak and reboot the DomU, you’ll notice messages like
XENUTIL: WARNING: CloseFrontend: timed out in XenbusWaitForBackendStateChange: /local/domain/0/backend/console/[id]/0 in state INITIALISING; retry. in your /var/log/xen/qemu-dm-*.log and Windows just gets stuck during boot and keeps spinning forever. To get it back to work, you’ll need to
after starting the VM (thanks to Keith Coleman‘s mailing list post!).
To automatically run these commands upon DomU start, create a script named /usr/lib/xen/bin/qemu-dm-citrixpv with the following contents
sh -c "sleep 10; xenstore-rm /local/domain/0/backend/console/$2; xenstore-rm /local/domain/0/backend/vfb/$2" &
exec /usr/lib/xen/bin/qemu-dm $*
chmod +x it.
Then, edit your DomU config file and modify the device_model line and point it to your new script:
device_model = '/usr/lib/xen/bin/qemu-dm-citrixpv'
Now your Windows Server 2008 R2 x64 HVM-DomU is all set!