Index: sys/dev/virtio/mmio/virtio_mmio.c
===================================================================
--- sys/dev/virtio/mmio/virtio_mmio.c
+++ sys/dev/virtio/mmio/virtio_mmio.c
@@ -1,11 +1,15 @@
 /*-
  * Copyright (c) 2014 Ruslan Bukin <br@bsdpad.com>
+ * Copyright (c) 2014 The FreeBSD Foundation
  * All rights reserved.
  *
  * This software was developed by SRI International and the University of
  * Cambridge Computer Laboratory under DARPA/AFRL contract (FA8750-10-C-0237)
  * ("CTSRD"), as part of the DARPA CRASH research programme.
  *
+ * Portions of this software were developed by Andrew Turner
+ * under sponsorship from the FreeBSD Foundation.
+ *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
@@ -131,15 +135,24 @@
 /*
  * I/O port read/write wrappers.
  */
-#define vtmmio_write_config_1(sc, o, v) \
-	bus_write_1((sc)->res[0], (o), (v)); \
-	VIRTIO_MMIO_NOTE(sc->platform, (o))
-#define vtmmio_write_config_2(sc, o, v) \
-	bus_write_2((sc)->res[0], (o), (v)); \
-	VIRTIO_MMIO_NOTE(sc->platform, (o))
-#define vtmmio_write_config_4(sc, o, v) \
-	bus_write_4((sc)->res[0], (o), (v)); \
-	VIRTIO_MMIO_NOTE(sc->platform, (o))
+#define vtmmio_write_config_1(sc, o, v)			\
+do {							\
+	bus_write_1((sc)->res[0], (o), (v)); 		\
+	if (sc->platform != NULL)			\
+		VIRTIO_MMIO_NOTE(sc->platform, (o));	\
+} while (0)
+#define vtmmio_write_config_2(sc, o, v)			\
+do {							\
+	bus_write_2((sc)->res[0], (o), (v));		\
+	if (sc->platform != NULL)			\
+		VIRTIO_MMIO_NOTE(sc->platform, (o));	\
+} while (0)
+#define vtmmio_write_config_4(sc, o, v)			\
+do {							\
+	bus_write_4((sc)->res[0], (o), (v));		\
+	if (sc->platform != NULL)			\
+		VIRTIO_MMIO_NOTE(sc->platform, (o));	\
+} while (0)
 
 #define vtmmio_read_config_1(sc, o) \
 	bus_read_1((sc)->res[0], (o))
@@ -200,11 +213,13 @@
 
 	sc = device_get_softc(dev);
 
-	err = VIRTIO_MMIO_SETUP_INTR(sc->platform, sc->dev,
-				vtmmio_vq_intr, sc);
-	if (err == 0) {
-		/* Okay we have backend-specific interrupts */
-		return (0);
+	if (sc->platform != NULL) {
+		err = VIRTIO_MMIO_SETUP_INTR(sc->platform, sc->dev,
+					vtmmio_vq_intr, sc);
+		if (err == 0) {
+			/* Okay we have backend-specific interrupts */
+			return (0);
+		}
 	}
 
 	rid = 0;
@@ -493,7 +508,7 @@
 		info = &vq_info[idx];
 
 		vtmmio_select_virtqueue(sc, idx);
-		size = vtmmio_read_config_2(sc, VIRTIO_MMIO_QUEUE_NUM);
+		size = vtmmio_read_config_4(sc, VIRTIO_MMIO_QUEUE_NUM_MAX);
 
 		error = virtqueue_alloc(dev, idx, size,
 		    VIRTIO_MMIO_VRING_ALIGN, 0xFFFFFFFFUL, info, &vq);
@@ -572,7 +587,7 @@
 
 	sc = device_get_softc(dev);
 
-	vtmmio_write_config_2(sc, VIRTIO_MMIO_QUEUE_NOTIFY, queue);
+	vtmmio_write_config_4(sc, VIRTIO_MMIO_QUEUE_NOTIFY, queue);
 }
 
 static uint8_t
@@ -582,7 +597,7 @@
 
 	sc = device_get_softc(dev);
 
-	return (vtmmio_read_config_1(sc, VIRTIO_MMIO_STATUS));
+	return (vtmmio_read_config_4(sc, VIRTIO_MMIO_STATUS));
 }
 
 static void
@@ -595,7 +610,7 @@
 	if (status != VIRTIO_CONFIG_STATUS_RESET)
 		status |= vtmmio_get_status(dev);
 
-	vtmmio_write_config_1(sc, VIRTIO_MMIO_STATUS, status);
+	vtmmio_write_config_4(sc, VIRTIO_MMIO_STATUS, status);
 }
 
 static void
@@ -611,13 +626,16 @@
 	off = VIRTIO_MMIO_CONFIG + offset;
 
 	for (d = dst; length > 0; d += size, off += size, length -= size) {
+#ifdef ALLOW_WORD_ALIGNED_ACCESS
 		if (length >= 4) {
 			size = 4;
 			*(uint32_t *)d = vtmmio_read_config_4(sc, off);
 		} else if (length >= 2) {
 			size = 2;
 			*(uint16_t *)d = vtmmio_read_config_2(sc, off);
-		} else {
+		} else
+#endif
+		{
 			size = 1;
 			*d = vtmmio_read_config_1(sc, off);
 		}
@@ -637,13 +655,16 @@
 	off = VIRTIO_MMIO_CONFIG + offset;
 
 	for (s = src; length > 0; s += size, off += size, length -= size) {
+#ifdef ALLOW_WORD_ALIGNED_ACCESS
 		if (length >= 4) {
 			size = 4;
 			vtmmio_write_config_4(sc, off, *(uint32_t *)s);
 		} else if (length >= 2) {
 			size = 2;
 			vtmmio_write_config_2(sc, off, *(uint16_t *)s);
-		} else {
+		} else
+#endif
+		{
 			size = 1;
 			vtmmio_write_config_1(sc, off, *s);
 		}
@@ -711,7 +732,7 @@
 	KASSERT(vq != NULL, ("%s: vq %d not allocated", __func__, idx));
 
 	vtmmio_select_virtqueue(sc, idx);
-	size = vtmmio_read_config_2(sc, VIRTIO_MMIO_QUEUE_NUM);
+	size = vtmmio_read_config_4(sc, VIRTIO_MMIO_QUEUE_NUM_MAX);
 
 	error = virtqueue_reinit(vq, size);
 	if (error)
@@ -778,7 +799,7 @@
 vtmmio_select_virtqueue(struct vtmmio_softc *sc, int idx)
 {
 
-	vtmmio_write_config_2(sc, VIRTIO_MMIO_QUEUE_SEL, idx);
+	vtmmio_write_config_4(sc, VIRTIO_MMIO_QUEUE_SEL, idx);
 }
 
 static void
@@ -787,14 +808,27 @@
 	struct vtmmio_virtqueue *vqx;
 	struct vtmmio_softc *sc;
 	struct virtqueue *vq;
+	uint32_t status;
 	int idx;
 
 	sc = arg;
 
+	status = vtmmio_read_config_4(sc, VIRTIO_MMIO_INTERRUPT_STATUS);
+	vtmmio_write_config_4(sc, VIRTIO_MMIO_INTERRUPT_ACK, status);
+
+	/* The config changed */
+	if (status & VIRTIO_MMIO_INT_CONFIG)
+		if (sc->vtmmio_child_dev != NULL)
+			VIRTIO_CONFIG_CHANGE(sc->vtmmio_child_dev);
+
 	/* Notify all virtqueues. */
-	for (idx = 0; idx < sc->vtmmio_nvqs; idx++) {
-		vqx = &sc->vtmmio_vqs[idx];
-		vq = vqx->vtv_vq;
-		virtqueue_intr(vq);
-	};
+	if (status & VIRTIO_MMIO_INT_VRING) {
+		for (idx = 0; idx < sc->vtmmio_nvqs; idx++) {
+			vqx = &sc->vtmmio_vqs[idx];
+			if (vqx->vtv_no_intr == 0) {
+				vq = vqx->vtv_vq;
+				virtqueue_intr(vq);
+			}
+		}
+	}
 }