/data/domains/windows/start_pci1.sh 0000:06.2.0
modprobe xen-pciback 'hide=(0000:06.2.0)'
xl pci-assignable-add 06.2.0

�..

Binding 0000:06.2.0 to pciback
/data/domains/windows/start_pci1.sh: line 17: echo: write error: Invalid
argument
/data/domains/windows/start_pci1.sh: line 18: echo: write error: No such
device
pci-assignable-add: malformed BDF specification �06.2.0"

That last error, and this page: http://wiki.xen.org/wiki/Bus:Device.Function_(BDF)_Notation  suggest that the parameter you pass into �xl pci-assignable-add' should be in the format �06:02.0� instead of �06.2.0�. The other errors might relate to poorly formatted PCI IDs as well: try �0000:06:02.0� ? 

However, I have no idea if that�s relevant. Haven�t used xen in a long time...

I also found this link while browsing: http://wiki.xen.org/wiki/Bind_lib.bash_:_A_script_that_makes_pciback_with_modules_easier_to_use.   Might help?