bus_alloc_resource_any failing to allocate irq for vmbus in amd64

Hi,
I am trying to use bus_alloc_resource_any() to allocate a irq line for vmbus but it is failing.

this is the patch :

+  sc->sc_vmbus_irid = 1;
+  device_t parent = device_get_parent(device_get_parent(sc->vmbus_dev));
+  sc->sc_vmbus_ires = bus_alloc_resource_any(parent,
+                                                   SYS_RES_IRQ, &(sc->sc_vmbus_irid), RF_ACTIVE|RF_SHAREABLE);
+   if (sc->sc_vmbus_ires == NULL) {
+           device_printf(sc->vmbus_dev, "could not allocate IRQ\n");
+           return (ENXIO);
+   }
+   error = bus_setup_intr(sc->vmbus_dev, sc->sc_vmbus_ires, INTR_TYPE_NET | INTR_MPSAFE,
+                                   NULL, vmbus_handle_intr_new, sc, &(sc->sc_vmbus_ihand));
+   if (error) {
+           device_printf(sc->vmbus_dev, "failed to setup IRQ\n");
+           if (bus_release_resource(sc->vmbus_dev, SYS_RES_IRQ, sc->sc_vmbus_irid, sc->sc_vmbus_ires))
+                   device_printf(sc->vmbus_dev, "could not release IRQ\n");
+           sc->sc_vmbus_ires = NULL;
+           return (error);
+   }

What am I missing here? Any help would be greatly appreciated.

Thanks & Regards,
Souradeep