[kernel-xen] xen-pciback in 3.9.x

[povder]

Hi again

I configured my system to work with xen-pciback as a module. Now I
didn't have any problems modprobing a module. I'm passing through some
USB devices and most importantly a VGA card (radeon 4850) as a
secondary VGA card to my HVM linux guest. I'm making devices
assignable by xl pci-assignable-add. I'm experiencing a significant
performance loss of my VGA card when compared to built in xen-pciback.
Honestly I didn't expect that change to module would impact
performance. I guess I'll ask on xen-users about it later.