Unfortunately this really looks like THE interrupt needs a full set of
IPI interrupt counters. For the moment, simply use a static throw-away
I'm really unsure what this should look like. The interrupt really should have per-core counters since it is expected to occur on all cores which process Xen events. Yet the intrng code only has a single per-interrupt counter, thus appearing to implicitly assume any given interrupt will only occur on one core which the interrupt has been assigned to.