Index: sys/dev/nvme/nvme_qpair.c
===================================================================
--- sys/dev/nvme/nvme_qpair.c
+++ sys/dev/nvme/nvme_qpair.c
@@ -583,13 +583,28 @@
 	}
 
 	while (1) {
-		cpl = qpair->cpl[qpair->cq_head];
+		uint16_t status;
 
-		/* Convert to host endian */
+		/*
+		 * We need to do this dance to avoid a race between the host and
+		 * the device where the device overtakes the host while the host
+		 * is reading this record, leaving the status field 'new' and the
+		 * sqhd and sqid potentially stale. If the phase doesn't match,
+		 * that means status hasn't yet been updated and we'll get any
+		 * pending changes next time. It also means that it must be the
+		 * same the second time. We have to sync before reading to ensure
+		 * any bouncing completes.
+		 */
+		status = le16toh(atomic_load_acq_16(&qpair->cpl[qpair->cq_head].status));
+		if (NVME_STATUS_GET_P(status) != qpair->phase)
+			break;
+
+		bus_dmamap_sync(qpair->dma_tag, qpair->queuemem_map,
+		    BUS_DMASYNC_POSTREAD | BUS_DMASYNC_POSTWRITE);
+		cpl = qpair->cpl[qpair->cq_head];
 		nvme_completion_swapbytes(&cpl);
 
-		if (NVME_STATUS_GET_P(cpl.status) != qpair->phase)
-			break;
+		KASSERT(status == cpl.status, ("received completion for unknown cmd"));
 
 		tr = qpair->act_tr[cpl.cid];