diff -r 488fbe994a6c -r 533feb86054b sys/dev/cxgbe/adapter.h
--- a/sys/dev/cxgbe/adapter.h	Wed Jun 14 19:36:28 2017 +0000
+++ b/sys/dev/cxgbe/adapter.h	Thu Jun 15 09:37:30 2017 -0700
@@ -647,7 +647,7 @@ struct sge_wrq {
 
 } __aligned(CACHE_LINE_SIZE);
 
-
+#define INVALID_NM_RXQ_CNTXT_ID ((uint16_t)(-1))
 struct sge_nm_rxq {
 	struct vi_info *vi;
 
@@ -680,6 +680,7 @@ struct sge_nm_rxq {
 	bus_addr_t fl_ba;
 } __aligned(CACHE_LINE_SIZE);
 
+#define INVALID_NM_TXQ_CNTXT_ID ((u_int)(-1))
 struct sge_nm_txq {
 	struct tx_desc *desc;
 	uint16_t cidx;
diff -r 488fbe994a6c -r 533feb86054b sys/dev/cxgbe/t4_netmap.c
--- a/sys/dev/cxgbe/t4_netmap.c	Wed Jun 14 19:36:28 2017 +0000
+++ b/sys/dev/cxgbe/t4_netmap.c	Thu Jun 15 09:37:30 2017 -0700
@@ -224,6 +224,7 @@ free_nm_rxq_hwq(struct vi_info *vi, stru
 	if (rc != 0)
 		device_printf(sc->dev, "%s: failed for iq %d, fl %d: %d\n",
 		    __func__, nm_rxq->iq_cntxt_id, nm_rxq->fl_cntxt_id, rc);
+	nm_rxq->iq_cntxt_id = INVALID_NM_RXQ_CNTXT_ID;
 	return (rc);
 }
 
@@ -310,6 +311,7 @@ free_nm_txq_hwq(struct vi_info *vi, stru
 	if (rc != 0)
 		device_printf(sc->dev, "%s: failed for eq %d: %d\n", __func__,
 		    nm_txq->cntxt_id, rc);
+	nm_txq->cntxt_id = INVALID_NM_TXQ_CNTXT_ID;
 	return (rc);
 }
 
@@ -318,6 +320,7 @@ cxgbe_netmap_on(struct adapter *sc, stru
     struct netmap_adapter *na)
 {
 	struct netmap_slot *slot;
+	struct netmap_kring *kring;
 	struct sge_nm_rxq *nm_rxq;
 	struct sge_nm_txq *nm_txq;
 	int rc, i, j, hwidx;
@@ -347,6 +350,11 @@ cxgbe_netmap_on(struct adapter *sc, stru
 	for_each_nm_rxq(vi, i, nm_rxq) {
 		struct irq *irq = &sc->irq[vi->first_intr + i];
 
+		kring = &na->rx_rings[nm_rxq->nid];
+		if (!nm_kring_pending_on(kring) ||
+		    nm_rxq->iq_cntxt_id != INVALID_NM_RXQ_CNTXT_ID)
+			continue;
+
 		alloc_nm_rxq_hwq(vi, nm_rxq, tnl_cong(vi->pi, nm_cong_drop));
 		nm_rxq->fl_hwidx = hwidx;
 		slot = netmap_reset(na, NR_RX, i, 0);
@@ -373,6 +381,11 @@ cxgbe_netmap_on(struct adapter *sc, stru
 	}
 
 	for_each_nm_txq(vi, i, nm_txq) {
+		kring = &na->tx_rings[nm_txq->nid];
+		if (!nm_kring_pending_on(kring) ||
+		    nm_txq->cntxt_id != INVALID_NM_TXQ_CNTXT_ID)
+			continue;
+
 		alloc_nm_txq_hwq(vi, nm_txq);
 		slot = netmap_reset(na, NR_TX, i, 0);
 		MPASS(slot != NULL);	/* XXXNM: error check, not assert */
@@ -401,6 +414,7 @@ static int
 cxgbe_netmap_off(struct adapter *sc, struct vi_info *vi, struct ifnet *ifp,
     struct netmap_adapter *na)
 {
+	struct netmap_kring *kring;
 	int rc, i;
 	struct sge_nm_txq *nm_txq;
 	struct sge_nm_rxq *nm_rxq;
@@ -419,6 +433,11 @@ cxgbe_netmap_off(struct adapter *sc, str
 	for_each_nm_txq(vi, i, nm_txq) {
 		struct sge_qstat *spg = (void *)&nm_txq->desc[nm_txq->sidx];
 
+		kring = &na->tx_rings[nm_txq->nid];
+		if (!nm_kring_pending_off(kring) ||
+		    nm_txq->cntxt_id == INVALID_NM_TXQ_CNTXT_ID)
+			continue;
+
 		/* Wait for hw pidx to catch up ... */
 		while (be16toh(nm_txq->pidx) != spg->pidx)
 			pause("nmpidx", 1);
@@ -432,6 +451,11 @@ cxgbe_netmap_off(struct adapter *sc, str
 	for_each_nm_rxq(vi, i, nm_rxq) {
 		struct irq *irq = &sc->irq[vi->first_intr + i];
 
+		kring = &na->rx_rings[nm_rxq->nid];
+		if (!nm_kring_pending_off(kring) ||
+		    nm_rxq->iq_cntxt_id == INVALID_NM_RXQ_CNTXT_ID)
+			continue;
+
 		while (!atomic_cmpset_int(&irq->nm_state, NM_ON, NM_OFF))
 			pause("nmst", 1);
 
diff -r 488fbe994a6c -r 533feb86054b sys/dev/cxgbe/t4_sge.c
--- a/sys/dev/cxgbe/t4_sge.c	Wed Jun 14 19:36:28 2017 +0000
+++ b/sys/dev/cxgbe/t4_sge.c	Thu Jun 15 09:37:30 2017 -0700
@@ -3264,6 +3264,7 @@ alloc_nm_rxq(struct vi_info *vi, struct 
 	nm_rxq->fl_pidx = nm_rxq->fl_cidx = 0;
 	nm_rxq->fl_sidx = na->num_rx_desc;
 	nm_rxq->intr_idx = intr_idx;
+	nm_rxq->iq_cntxt_id = INVALID_NM_RXQ_CNTXT_ID;
 
 	ctx = &vi->ctx;
 	children = SYSCTL_CHILDREN(oid);
@@ -3305,6 +3306,8 @@ free_nm_rxq(struct vi_info *vi, struct s
 {
 	struct adapter *sc = vi->pi->adapter;
 
+	MPASS(nm_rxq->iq_cntxt_id == INVALID_NM_RXQ_CNTXT_ID);
+
 	free_ring(sc, nm_rxq->iq_desc_tag, nm_rxq->iq_desc_map, nm_rxq->iq_ba,
 	    nm_rxq->iq_desc);
 	free_ring(sc, nm_rxq->fl_desc_tag, nm_rxq->fl_desc_map, nm_rxq->fl_ba,
@@ -3339,6 +3342,7 @@ alloc_nm_txq(struct vi_info *vi, struct 
 	    V_TXPKT_INTF(pi->tx_chan) | V_TXPKT_PF(G_FW_VIID_PFN(vi->viid)) |
 	    V_TXPKT_VF(G_FW_VIID_VIN(vi->viid)) |
 	    V_TXPKT_VF_VLD(G_FW_VIID_VIVLD(vi->viid)));
+	nm_txq->cntxt_id = INVALID_NM_TXQ_CNTXT_ID;
 
 	snprintf(name, sizeof(name), "%d", idx);
 	oid = SYSCTL_ADD_NODE(&vi->ctx, children, OID_AUTO, name, CTLFLAG_RD,
@@ -3362,6 +3366,8 @@ free_nm_txq(struct vi_info *vi, struct s
 {
 	struct adapter *sc = vi->pi->adapter;
 
+	MPASS(nm_txq->cntxt_id == INVALID_NM_TXQ_CNTXT_ID);
+
 	free_ring(sc, nm_txq->desc_tag, nm_txq->desc_map, nm_txq->ba,
 	    nm_txq->desc);