Xen users - Sep 2012 - Intel igb driver 3.2.10-k failed to work on Xen 4.1.2 kernel

Hi,

I tried to use Intel quad-port ethernet adapter on a server running 
Ubuntu 12.04.1 (kernel 3.2.27), but the igb driver (version 3.2.10-k) 
failed to work on Xen 4.1.2 kernel in bridge mode.

The content of /etc/network/interfaces follows :-

auto xenbr0
iface xenbr0 inet static
	address .....
	......
	bridge_ports eth0

auto eth0
iface eth0 inet manual

I checked with brctl and there was no associated interface (i.e. eth0 
was missing). The bridge interface appeared to be up and running but no 
traffic could go through (e.g. ping failed). I tried to add the 2nd 
ethernet port to the bridge and the command completed successfully, but 
still no traffic could pass through.

The igb driver worked normally when booted to kernel 3.2.27 (not Xen 
kernel).

I hope someone could advise what went wrong and how to fix it.

Thanks a lot.

John Mok