Index: legacy_irq.c
===================================================================
--- legacy_irq.c	(revision 258570)
+++ legacy_irq.c	(working copy)
@@ -58,7 +58,8 @@
 {
 	int i;
 
-	assert(irq < NLIRQ);
+	if (irq >= NLIRQ)
+		return (irq);
 
 	if (irq < 0) {
 		for (i = 0; i < NLIRQ; i++) {
Index: pci_virtio_block.c
===================================================================
--- pci_virtio_block.c	(revision 258570)
+++ pci_virtio_block.c	(working copy)
@@ -117,6 +117,7 @@
  */
 struct pci_vtblk_softc {
 	struct virtio_softc vbsc_vs;
+	pthread_mutex_t vsc_mtx;
 	struct vqueue_info vbsc_vq;
 	int		vbsc_fd;
 	struct vtblk_config vbsc_cfg;	
@@ -304,8 +305,12 @@
 	/* record fd of storage device/file */
 	sc->vbsc_fd = fd;
 
+	pthread_mutex_init(&sc->vsc_mtx, NULL);
+
 	/* init virtio softc and virtqueues */
 	vi_softc_linkup(&sc->vbsc_vs, &vtblk_vi_consts, sc, pi, &sc->vbsc_vq);
+	sc->vbsc_vs.vs_mtx = &sc->vsc_mtx;
+
 	sc->vbsc_vq.vq_qsize = VTBLK_RINGSZ;
 	/* sc->vbsc_vq.vq_notify = we have no per-queue notify */
 
@@ -339,6 +344,8 @@
 	pci_set_cfgdata8(pi, PCIR_CLASS, PCIC_STORAGE);
 	pci_set_cfgdata16(pi, PCIR_SUBDEV_0, VIRTIO_TYPE_BLOCK);
 
+	pci_lintr_request(pi, 20);
+
 	if (vi_intr_init(&sc->vbsc_vs, 1, fbsdrun_virtio_msix()))
 		return (1);
 	vi_set_io_bar(&sc->vbsc_vs, 0);
Index: pci_virtio_net.c
===================================================================
--- pci_virtio_net.c	(revision 258570)
+++ pci_virtio_net.c	(working copy)
@@ -519,6 +519,8 @@
 	pthread_mutex_init(&sc->vsc_mtx, NULL);
 
 	vi_softc_linkup(&sc->vsc_vs, &vtnet_vi_consts, sc, pi, sc->vsc_queues);
+	sc->vsc_vs.vs_mtx = &sc->vsc_mtx;
+
 	sc->vsc_queues[VTNET_RXQ].vq_qsize = VTNET_RINGSZ;
 	sc->vsc_queues[VTNET_RXQ].vq_notify = pci_vtnet_ping_rxq;
 	sc->vsc_queues[VTNET_TXQ].vq_qsize = VTNET_RINGSZ;
@@ -608,6 +610,8 @@
 	pci_set_cfgdata8(pi, PCIR_CLASS, PCIC_NETWORK);
 	pci_set_cfgdata16(pi, PCIR_SUBDEV_0, VIRTIO_TYPE_NET);
 
+	pci_lintr_request(pi, 20);
+
 	/* link always up */
 	sc->vsc_config.status = 1;
 	
Index: virtio.c
===================================================================
--- virtio.c	(revision 258570)
+++ virtio.c	(working copy)
@@ -99,7 +99,11 @@
 	vs->vs_negotiated_caps = 0;
 	vs->vs_curq = 0;
 	/* vs->vs_status = 0; -- redundant */
+	VS_LOCK(vs);
+	if (vs->vs_isr)
+		pci_lintr_deassert(vs->vs_pi);
 	vs->vs_isr = 0;
+	VS_UNLOCK(vs);
 	vs->vs_msix_cfg_idx = VIRTIO_MSI_NO_VECTOR;
 }
 
@@ -139,8 +143,10 @@
 			return (1);
 	} else {
 		vs->vs_flags &= ~VIRTIO_USE_MSIX;
+#if 0
 		/* Only 1 MSI vector for bhyve */
 		pci_emul_add_msicap(vs->vs_pi, 1);
+#endif
 	}
 	return (0);
 }
@@ -591,6 +597,8 @@
 	case VTCFG_R_ISR:
 		value = vs->vs_isr;
 		vs->vs_isr = 0;		/* a read clears this flag */
+		if (value)
+			pci_lintr_deassert(pi);
 		break;
 	case VTCFG_R_CFGVEC:
 		value = vs->vs_msix_cfg_idx;
Index: virtio.h
===================================================================
--- virtio.h	(revision 258570)
+++ virtio.h	(working copy)
@@ -328,6 +328,18 @@
 	uint16_t vs_msix_cfg_idx;	/* MSI-X vector for config event */
 };
 
+#define	VS_LOCK(vs)							\
+do {									\
+	if (vs->vs_mtx)							\
+		pthread_mutex_lock(vs->vs_mtx);				\
+} while (0)
+
+#define	VS_UNLOCK(vs)							\
+do {									\
+	if (vs->vs_mtx)							\
+		pthread_mutex_unlock(vs->vs_mtx);			\
+} while (0)
+
 struct virtio_consts {
 	const char *vc_name;		/* name of driver (for diagnostics) */
 	int	vc_nvq;			/* number of virtual queues */
@@ -434,8 +446,10 @@
 	if (vs->vs_flags & VIRTIO_USE_MSIX)
 		pci_generate_msix(vs->vs_pi, vq->vq_msix_idx);
 	else {
+		VS_LOCK(vs);
 		vs->vs_isr |= VTCFG_ISR_QUEUES;
-		pci_generate_msi(vs->vs_pi, 0);
+		pci_lintr_assert(vs->vs_pi);
+		VS_UNLOCK(vs);
 	}
 }