Suspend with XEN?

Hi,

I am working with Xen on my laptop running Ubuntu 12.04. I wonder if there are any ways to suspend/hibernate while running Xen? Currently if I use pm-suspend, the machines goes to suspend as usual but cannot wake up, black screen appears. To note that my machine can suspend/hibernate normally before installing Xen.
I have searched around for this issue but nothing seemed positive.

Any help is appreciated. Thanks!