From: "Manuel Bouyer" <bouyer@antioche.lip6.fr>
> Hum, I need to look at this again. From what I remember, if I leaved
> the events blocked, HYPERVISOR_yield() would never return.
> But maybe I had something else wrong in my code.

HYPERVISOR_yield() should be used to yield the cpu, i.e. other domains will 
get to run and the current domain gets put on the runqueue and will run 
again at some point.  HYPERVISOR_block() will also yield the cpu but only 
returns once there's an event that can be delivered.

     christian