vfio: abort if an emulated iommu is used

vfio doesn't support guest iommus yet, indicate it to the user
by gently depositing a core on their disk.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Avi Kivity <avi.kivity@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

hw/misc/vfio.c

@@ -1939,6 +1939,8 @@ static void vfio_listener_region_add(MemoryListener *listener,
     void *vaddr;
     int ret;
 
+    assert(!memory_region_is_iommu(section->mr));
+
     if (vfio_listener_skipped_section(section)) {
         DPRINTF("SKIPPING region_add %"HWADDR_PRIx" - %"PRIx64"\n",
                 section->offset_within_address_space,