Index: sys/dev/mrsas/mrsas.c
===================================================================
--- sys/dev/mrsas/mrsas.c
+++ sys/dev/mrsas/mrsas.c
@@ -2782,8 +2782,12 @@
 	init_frame->queue_info_new_phys_addr_lo = htole32(phys_addr);
 	init_frame->data_xfer_len = htole32(sizeof(Mpi2IOCInitRequest_t));
 
-	req_desc.addr.u.low = htole32((bus_addr_t)sc->ioc_init_phys_mem & 0xFFFFFFFF);
-	req_desc.addr.u.high = htole32((bus_addr_t)sc->ioc_init_phys_mem >> 32);
+	if (sizeof(bus_addr_t) == sizeof(uint32_t))
+		req_desc.addr.Words = htole32((bus_addr_t)sc->ioc_init_phys_mem);
+	else if (sizeof(bus_addr_t) == sizeof(uint64_t))
+		req_desc.addr.Words = htole64((bus_addr_t)sc->ioc_init_phys_mem);
+	else
+		panic("mrsas: unhandled bus_addr_t size");
 
 	req_desc.MFAIo.RequestFlags =
 	    (MRSAS_REQ_DESCRIPT_FLAGS_MFA << MRSAS_REQ_DESCRIPT_FLAGS_TYPE_SHIFT);