The problem you're having is essentially the same as the user-level
interrupt handler problem I've been dealing with for ages.

The basic rule is: don't share interrupts between devices on the host
and devices in the guest.  But you *can* share interrupts between
devices in a single guest.

If you want the code, see
http://www.gelato.unsw.edu.au/cgi-bin/viewvc.cgi/cvs/kernel/usrdrivers/latest/
and look at generic-irq.patch and fasync (which adds asynchronous notifications)

For the KVM work it'll need modifying a little, but the basic
infrastructure is there.

We've currently got this working to pass interrupts to a type-II (hosted)
virtual machine monitor running a guest kernel with native drivers.

--
Dr Peter Chubb  http://www.gelato.unsw.edu.au  peterc AT gelato.unsw.edu.au
http://www.ertos.nicta.com.au           ERTOS within National ICT Australia
-