Index: sys/dev/virtio/scsi/virtio_scsi.c
===================================================================
--- sys/dev/virtio/scsi/virtio_scsi.c
+++ sys/dev/virtio/scsi/virtio_scsi.c
@@ -286,6 +286,7 @@
 
 	VTSCSI_LOCK_INIT(sc, device_get_nameunit(dev));
 	TAILQ_INIT(&sc->vtscsi_req_free);
+	TAILQ_INIT(&sc->vtscsi_resrc_pend);
 
 	vtscsi_get_tunables(sc);
 	vtscsi_setup_sysctl(sc);
@@ -751,7 +752,10 @@
 
 	switch (ccbh->func_code) {
 	case XPT_SCSI_IO:
-		vtscsi_cam_scsi_io(sc, sim, ccb);
+		if (!TAILQ_EMPTY(&sc->vtscsi_resrc_pend))
+			TAILQ_INSERT_TAIL(&sc->vtscsi_resrc_pend, ccbh, sim_links.tqe);
+		else
+			vtscsi_cam_scsi_io(sc, sim, ccb);
 		break;
 
 	case XPT_SET_TRAN_SETTINGS:
@@ -1129,10 +1133,11 @@
 	if (error) {
 		vtscsi_dprintf(sc, VTSCSI_ERROR,
 		    "enqueue error=%d req=%p ccb=%p\n", error, req, ccbh);
-
-		ccbh->status = CAM_REQUEUE_REQ;
-		vtscsi_freeze_simq(sc, VTSCSI_REQUEST_VQ);
-		return (error);
+		ccbh->sim_priv.entries[0].field = (readable + writable);
+		vtscsi_enqueue_request(sc, req);
+		TAILQ_INSERT_TAIL(&sc->vtscsi_resrc_pend, ccbh, sim_links.tqe);
+		sc->vtscsi_stats.num_pends++;
+		return 0;
 	}
 
 	ccbh->status |= CAM_SIM_QUEUED;
@@ -1383,6 +1388,7 @@
 	struct ccb_scsiio *csio;
 	struct virtio_scsi_cmd_resp *cmd_resp;
 	cam_status status;
+	uint16_t nfree;
 
 	csio = &req->vsr_ccb->csio;
 	ccbh = &csio->ccb_h;
@@ -1415,6 +1421,16 @@
 	ccbh->status = status;
 	xpt_done(req->vsr_ccb);
 	vtscsi_enqueue_request(sc, req);
+	while (!TAILQ_EMPTY(&sc->vtscsi_resrc_pend)) {
+		ccbh = TAILQ_FIRST(&sc->vtscsi_resrc_pend);
+		nfree = virtqueue_nfree(sc->vtscsi_request_vq);
+		if (nfree >= ccbh->sim_priv.entries[0].field) {
+			TAILQ_REMOVE(&sc->vtscsi_resrc_pend, ccbh, sim_links.tqe);
+			vtscsi_cam_scsi_io(sc, sc->vtscsi_sim, (union ccb *)ccbh);
+		} else
+			/* Can't satisfy the request. */
+			break;
+	}
 }
 
 static void
@@ -2329,6 +2345,8 @@
 	SYSCTL_ADD_ULONG(ctx, child, OID_AUTO, "dequeue_no_requests",
 	    CTLFLAG_RD, &stats->dequeue_no_requests,
 	    "No available requests to dequeue");
+	SYSCTL_ADD_ULONG(ctx, child, OID_AUTO, "num_pends", CTLFLAG_RD,
+	    &stats->num_pends, "SCSI commands pended");
 }
 
 static void
Index: sys/dev/virtio/scsi/virtio_scsivar.h
===================================================================
--- sys/dev/virtio/scsi/virtio_scsivar.h
+++ sys/dev/virtio/scsi/virtio_scsivar.h
@@ -40,6 +40,7 @@
 struct vtscsi_statistics {
 	unsigned long		scsi_cmd_timeouts;
 	unsigned long		dequeue_no_requests;
+	unsigned long		num_pends;
 };
 
 struct vtscsi_softc {
@@ -83,6 +84,8 @@
 	struct virtio_scsi_event
 				 vtscsi_event_bufs[VTSCSI_NUM_EVENT_BUFS];
 
+	TAILQ_HEAD(,ccb_hdr)	 vtscsi_resrc_pend;
+
 	struct vtscsi_statistics vtscsi_stats;
 };