Index: sys/dev/nvme/nvme_qpair.c
===================================================================
--- sys/dev/nvme/nvme_qpair.c	(revision 336931)
+++ sys/dev/nvme/nvme_qpair.c	(working copy)
@@ -401,6 +401,8 @@
 		req->retries++;
 		nvme_qpair_submit_tracker(qpair, tr);
 	} else {
+	    	bus_dmamap_sync(qpair->dma_tag_payload, tr->payload_dma_map,
+		    BUS_DMASYNC_POSTREAD | BUS_DMASYNC_POSTWRITE);
 		if (req->type != NVME_REQUEST_NULL)
 			bus_dmamap_unload(qpair->dma_tag_payload,
 			    tr->payload_dma_map);
@@ -487,15 +489,17 @@
 		 */
 		return (false);
 
+	bus_dmamap_sync(qpair->dma_tag, qpair->queuemem_map,
+	    BUS_DMASYNC_POSTREAD | BUS_DMASYNC_POSTWRITE);
 	while (1) {
 		cpl = qpair->cpl[qpair->cq_head];
 
+		if (!!(cpl.status & htole16(NVME_STATUS_P_MASK)) != qpair->phase)
+			break;
+
 		/* Convert to host endian */
 		nvme_completion_swapbytes(&cpl);
 
-		if (NVME_STATUS_GET_P(cpl.status) != qpair->phase)
-			break;
-
 		tr = qpair->act_tr[cpl.cid];
 
 		if (tr != NULL) {
@@ -822,6 +826,8 @@
 		    nvme_timeout, tr);
 #endif
 
+	bus_dmamap_sync(qpair->dma_tag, qpair->queuemem_map,
+	    BUS_DMASYNC_PREREAD | BUS_DMASYNC_PREWRITE);
 	/* Copy the command from the tracker to the submission queue. */
 	memcpy(&qpair->cmd[qpair->sq_tail], &req->cmd, sizeof(req->cmd));
 
@@ -879,6 +885,8 @@
 		tr->req->cmd.prp2 = 0;
 	}
 
+	bus_dmamap_sync(tr->qpair->dma_tag_payload, tr->payload_dma_map,
+	    BUS_DMASYNC_PREREAD | BUS_DMASYNC_PREWRITE);
 	nvme_qpair_submit_tracker(tr->qpair, tr);
 }