Index: head/sys/dev/sfxge/sfxge.h
===================================================================
--- head/sys/dev/sfxge/sfxge.h
+++ head/sys/dev/sfxge/sfxge.h
@@ -294,6 +294,8 @@
 	efx_nic_t			*enp;
 	efsys_lock_t			enp_lock;
 
+	boolean_t			txq_dynamic_cksum_toggle_supported;
+
 	unsigned int			rxq_entries;
 	unsigned int			txq_entries;
 
Index: head/sys/dev/sfxge/sfxge.c
===================================================================
--- head/sys/dev/sfxge/sfxge.c
+++ head/sys/dev/sfxge/sfxge.c
@@ -762,6 +762,11 @@
 	}
 	sc->rxq_entries = sfxge_rx_ring_entries;
 
+	if (efx_nic_cfg_get(enp)->enc_features & EFX_FEATURE_TXQ_CKSUM_OP_DESC)
+		sc->txq_dynamic_cksum_toggle_supported = B_TRUE;
+	else
+		sc->txq_dynamic_cksum_toggle_supported = B_FALSE;
+
 	if (!ISP2(sfxge_tx_ring_entries) ||
 	    (sfxge_tx_ring_entries < EFX_TXQ_MINNDESCS) ||
 	    (sfxge_tx_ring_entries > efx_nic_cfg_get(enp)->enc_txq_max_ndescs)) {
Index: head/sys/dev/sfxge/sfxge_ev.c
===================================================================
--- head/sys/dev/sfxge/sfxge_ev.c
+++ head/sys/dev/sfxge/sfxge_ev.c
@@ -269,8 +269,11 @@
 {
 	unsigned int index;
 
-	KASSERT((evq->index == 0 && label < SFXGE_EVQ0_N_TXQ(evq->sc)) ||
-	    (label == SFXGE_TXQ_IP_TCP_UDP_CKSUM), ("unexpected txq label"));
+	KASSERT((evq->sc->txq_dynamic_cksum_toggle_supported) ? (label == 0) :
+		((evq->index == 0 && label < SFXGE_TXQ_NTYPES) ||
+		 (label == SFXGE_TXQ_IP_TCP_UDP_CKSUM)),
+		("unexpected txq label"));
+
 	index = (evq->index == 0) ?
 		label : (evq->index - 1 + SFXGE_EVQ0_N_TXQ(evq->sc));
 	return (evq->sc->txq[index]);
Index: head/sys/dev/sfxge/sfxge_tx.h
===================================================================
--- head/sys/dev/sfxge/sfxge_tx.h
+++ head/sys/dev/sfxge/sfxge_tx.h
@@ -139,7 +139,9 @@
 	SFXGE_TXQ_NTYPES
 };
 
-#define	SFXGE_EVQ0_N_TXQ(_sc)	SFXGE_TXQ_NTYPES
+#define	SFXGE_EVQ0_N_TXQ(_sc)						\
+	((_sc)->txq_dynamic_cksum_toggle_supported ?			\
+	1 : SFXGE_TXQ_NTYPES)
 
 #define	SFXGE_TXQ_UNBLOCK_LEVEL(_entries)	(EFX_TXQ_LIMIT(_entries) / 4)
 
@@ -205,6 +207,9 @@
 	unsigned int			n_pend_desc;
 	unsigned int			added;
 	unsigned int			reaped;
+
+	/* The last (or constant) set of HW offloads requested on the queue */
+	uint16_t			hw_cksum_flags;
 
 	/* The last VLAN TCI seen on the queue if FW-assisted tagging is
 	   used */
Index: head/sys/dev/sfxge/sfxge_tx.c
===================================================================
--- head/sys/dev/sfxge/sfxge_tx.c
+++ head/sys/dev/sfxge/sfxge_tx.c
@@ -35,7 +35,7 @@
 
 /* Theory of operation:
  *
- * Tx queues allocation and mapping
+ * Tx queues allocation and mapping on Siena
  *
  * One Tx queue with enabled checksum offload is allocated per Rx channel
  * (event queue).  Also 2 Tx queues (one without checksum offload and one
@@ -46,6 +46,17 @@
  *	if event queue index is 0, TxQ-index = TxQ-label * [0..SFXGE_TXQ_NTYPES)
  *	else TxQ-index = SFXGE_TXQ_NTYPES + EvQ-index - 1
  * See sfxge_get_txq_by_label() sfxge_ev.c
+ *
+ * Tx queue allocation and mapping on EF10
+ *
+ * One Tx queue with enabled checksum offload is allocated per Rx
+ * channel (event queue). Checksum offload on all Tx queues is enabled or
+ * disabled dynamically by inserting option descriptors, so the additional
+ * queues used on Siena are not required.
+ *
+ * TxQ label is always set to zero on EF10 hardware.
+ * So, event queue to Tx queue mapping is simple:
+ * TxQ-index = EvQ-index
  */
 
 #include <sys/cdefs.h>
@@ -139,38 +150,75 @@
 static void sfxge_tx_qunblock(struct sfxge_txq *txq);
 static int sfxge_tx_queue_tso(struct sfxge_txq *txq, struct mbuf *mbuf,
 			      const bus_dma_segment_t *dma_seg, int n_dma_seg,
-			      int vlan_tagged);
+			      int n_extra_descs);
 
+static inline void
+sfxge_next_stmp(struct sfxge_txq *txq, struct sfxge_tx_mapping **pstmp)
+{
+	KASSERT((*pstmp)->flags == 0, ("stmp flags are not 0"));
+	if (__predict_false(*pstmp ==
+			    &txq->stmp[txq->ptr_mask]))
+		*pstmp = &txq->stmp[0];
+	else
+		(*pstmp)++;
+}
+
 static int
-sfxge_tx_maybe_insert_tag(struct sfxge_txq *txq, struct mbuf *mbuf)
+sfxge_tx_maybe_toggle_cksum_offload(struct sfxge_txq *txq, struct mbuf *mbuf,
+				    struct sfxge_tx_mapping **pstmp)
 {
+	uint16_t new_hw_cksum_flags;
+	efx_desc_t *desc;
+
+	if (mbuf->m_pkthdr.csum_flags &
+	    (CSUM_DELAY_DATA | CSUM_DELAY_DATA_IPV6 | CSUM_TSO)) {
+		/*
+		 * We always set EFX_TXQ_CKSUM_IPV4 here because this
+		 * configuration is the most useful, and this won't
+		 * cause any trouble in case of IPv6 traffic anyway.
+		 */
+		new_hw_cksum_flags = EFX_TXQ_CKSUM_IPV4 | EFX_TXQ_CKSUM_TCPUDP;
+	} else if (mbuf->m_pkthdr.csum_flags & CSUM_DELAY_IP) {
+		new_hw_cksum_flags = EFX_TXQ_CKSUM_IPV4;
+	} else {
+		new_hw_cksum_flags = 0;
+	}
+
+	if (new_hw_cksum_flags == txq->hw_cksum_flags)
+		return (0);
+
+	desc = &txq->pend_desc[txq->n_pend_desc];
+	efx_tx_qdesc_checksum_create(txq->common, new_hw_cksum_flags, desc);
+	txq->hw_cksum_flags = new_hw_cksum_flags;
+	txq->n_pend_desc++;
+
+	sfxge_next_stmp(txq, pstmp);
+
+	return (1);
+}
+
+static int
+sfxge_tx_maybe_insert_tag(struct sfxge_txq *txq, struct mbuf *mbuf,
+			  struct sfxge_tx_mapping **pstmp)
+{
 	uint16_t this_tag = ((mbuf->m_flags & M_VLANTAG) ?
 			     mbuf->m_pkthdr.ether_vtag :
 			     0);
+	efx_desc_t *desc;
 
 	if (this_tag == txq->hw_vlan_tci)
 		return (0);
 
-	efx_tx_qdesc_vlantci_create(txq->common,
-				    bswap16(this_tag),
-				    &txq->pend_desc[0]);
-	txq->n_pend_desc = 1;
+	desc = &txq->pend_desc[txq->n_pend_desc];
+	efx_tx_qdesc_vlantci_create(txq->common, bswap16(this_tag), desc);
 	txq->hw_vlan_tci = this_tag;
+	txq->n_pend_desc++;
+
+	sfxge_next_stmp(txq, pstmp);
+
 	return (1);
 }
 
-static inline void
-sfxge_next_stmp(struct sfxge_txq *txq, struct sfxge_tx_mapping **pstmp)
-{
-	KASSERT((*pstmp)->flags == 0, ("stmp flags are not 0"));
-	if (__predict_false(*pstmp ==
-			    &txq->stmp[txq->ptr_mask]))
-		*pstmp = &txq->stmp[0];
-	else
-		(*pstmp)++;
-}
-
-
 void
 sfxge_tx_qcomplete(struct sfxge_txq *txq, struct sfxge_evq *evq)
 {
@@ -361,8 +409,9 @@
 	int rc;
 	int i;
 	int eop;
+	uint16_t hw_cksum_flags_prev;
 	uint16_t hw_vlan_tci_prev;
-	int vlan_tagged;
+	int n_extra_descs;
 
 	KASSERT(!txq->blocked, ("txq->blocked"));
 
@@ -413,14 +462,20 @@
 
 	used_map = &stmp->map;
 
+	hw_cksum_flags_prev = txq->hw_cksum_flags;
 	hw_vlan_tci_prev = txq->hw_vlan_tci;
 
-	vlan_tagged = sfxge_tx_maybe_insert_tag(txq, mbuf);
-	if (vlan_tagged) {
-		sfxge_next_stmp(txq, &stmp);
-	}
+	/*
+	 * The order of option descriptors, which are used to leverage VLAN tag
+	 * and checksum offloads, might be important. Changing checksum offload
+	 * between VLAN option and packet descriptors probably does not work.
+	 */
+	n_extra_descs = sfxge_tx_maybe_toggle_cksum_offload(txq, mbuf, &stmp);
+	n_extra_descs += sfxge_tx_maybe_insert_tag(txq, mbuf, &stmp);
+
 	if (mbuf->m_pkthdr.csum_flags & CSUM_TSO) {
-		rc = sfxge_tx_queue_tso(txq, mbuf, dma_seg, n_dma_seg, vlan_tagged);
+		rc = sfxge_tx_queue_tso(txq, mbuf, dma_seg, n_dma_seg,
+					n_extra_descs);
 		if (rc < 0)
 			goto reject_mapped;
 		stmp = &txq->stmp[(rc - 1) & txq->ptr_mask];
@@ -431,7 +486,7 @@
 
 		i = 0;
 		for (;;) {
-			desc = &txq->pend_desc[i + vlan_tagged];
+			desc = &txq->pend_desc[i + n_extra_descs];
 			eop = (i == n_dma_seg - 1);
 			efx_tx_qdesc_dma_create(txq->common,
 						dma_seg[i].ds_addr,
@@ -443,7 +498,7 @@
 			i++;
 			sfxge_next_stmp(txq, &stmp);
 		}
-		txq->n_pend_desc = n_dma_seg + vlan_tagged;
+		txq->n_pend_desc = n_dma_seg + n_extra_descs;
 	}
 
 	/*
@@ -467,6 +522,7 @@
 
 reject_mapped:
 	txq->hw_vlan_tci = hw_vlan_tci_prev;
+	txq->hw_cksum_flags = hw_cksum_flags_prev;
 	bus_dmamap_unload(txq->packet_dma_tag, *used_map);
 reject:
 	/* Drop the packet on the floor. */
@@ -840,8 +896,9 @@
 		("interface not up"));
 
 	/* Pick the desired transmit queue. */
-	if (m->m_pkthdr.csum_flags &
-	    (CSUM_DELAY_DATA | CSUM_TCP_IPV6 | CSUM_UDP_IPV6 | CSUM_TSO)) {
+	if (sc->txq_dynamic_cksum_toggle_supported |
+	    (m->m_pkthdr.csum_flags &
+	     (CSUM_DELAY_DATA | CSUM_TCP_IPV6 | CSUM_UDP_IPV6 | CSUM_TSO))) {
 		int index = 0;
 
 #ifdef RSS
@@ -867,7 +924,9 @@
 		if (m->m_pkthdr.csum_flags & CSUM_TSO)
 			sfxge_parse_tx_packet(m);
 #endif
-		txq = sc->txq[SFXGE_TXQ_IP_TCP_UDP_CKSUM + index];
+		index += (sc->txq_dynamic_cksum_toggle_supported == B_FALSE) ?
+			 SFXGE_TXQ_IP_TCP_UDP_CKSUM : 0;
+		txq = sc->txq[index];
 	} else if (m->m_pkthdr.csum_flags & CSUM_DELAY_IP) {
 		txq = sc->txq[SFXGE_TXQ_IP_CKSUM];
 	} else {
@@ -1311,7 +1370,7 @@
 static int
 sfxge_tx_queue_tso(struct sfxge_txq *txq, struct mbuf *mbuf,
 		   const bus_dma_segment_t *dma_seg, int n_dma_seg,
-		   int vlan_tagged)
+		   int n_extra_descs)
 {
 	struct sfxge_tso_state tso;
 	unsigned int id;
@@ -1328,7 +1387,7 @@
 	tso.in_len = dma_seg->ds_len - (tso.header_len - skipped);
 	tso.dma_addr = dma_seg->ds_addr + (tso.header_len - skipped);
 
-	id = (txq->added + vlan_tagged) & txq->ptr_mask;
+	id = (txq->added + n_extra_descs) & txq->ptr_mask;
 	if (__predict_false(tso_start_new_packet(txq, &tso, &id)))
 		return (-1);
 
@@ -1492,6 +1551,8 @@
 	efx_sram_buf_tbl_clear(sc->enp, txq->buf_base_id,
 	    EFX_TXQ_NBUFS(sc->txq_entries));
 
+	txq->hw_cksum_flags = 0;
+
 	SFXGE_EVQ_UNLOCK(evq);
 	SFXGE_TXQ_UNLOCK(txq);
 }
@@ -1513,6 +1574,10 @@
 	unsigned int fa_tso_v1_max_descs = 0;
 	unsigned int fa_tso_v2_max_descs = 0;
 
+	/* Checksum offload Tx option descriptor may be required */
+	if (sc->txq_dynamic_cksum_toggle_supported)
+		max_descs++;
+
 	/* VLAN tagging Tx option descriptor may be required */
 	if (efx_nic_cfg_get(sc->enp)->enc_hw_tx_insert_vlan_enabled)
 		max_descs++;
@@ -1557,6 +1622,7 @@
 	efsys_mem_t *esmp;
 	uint16_t flags;
 	unsigned int tso_fw_assisted;
+	unsigned int label;
 	struct sfxge_evq *evq;
 	unsigned int desc_index;
 	int rc;
@@ -1598,8 +1664,10 @@
 		break;
 	}
 
+	label = (sc->txq_dynamic_cksum_toggle_supported) ? 0 : txq->type;
+
 	/* Create the common code transmit queue. */
-	if ((rc = efx_tx_qcreate(sc->enp, index, txq->type, esmp,
+	if ((rc = efx_tx_qcreate(sc->enp, index, label, esmp,
 	    sc->txq_entries, txq->buf_base_id, flags, evq->common,
 	    &txq->common, &desc_index)) != 0) {
 		/* Retry if no FATSOv2 resources, otherwise fail */
@@ -1609,7 +1677,7 @@
 		/* Looks like all FATSOv2 contexts are used */
 		flags &= ~EFX_TXQ_FATSOV2;
 		tso_fw_assisted &= ~SFXGE_FATSOV2;
-		if ((rc = efx_tx_qcreate(sc->enp, index, txq->type, esmp,
+		if ((rc = efx_tx_qcreate(sc->enp, index, label, esmp,
 		    sc->txq_entries, txq->buf_base_id, flags, evq->common,
 		    &txq->common, &desc_index)) != 0)
 			goto fail;
@@ -1632,6 +1700,9 @@
 
 	txq->hw_vlan_tci = 0;
 
+	txq->hw_cksum_flags = flags &
+			      (EFX_TXQ_CKSUM_IPV4 | EFX_TXQ_CKSUM_TCPUDP);
+
 	SFXGE_TXQ_UNLOCK(txq);
 
 	return (0);
@@ -1993,13 +2064,15 @@
 	}
 
 	/* Initialize the transmit queues */
-	if ((rc = sfxge_tx_qinit(sc, SFXGE_TXQ_NON_CKSUM,
-	    SFXGE_TXQ_NON_CKSUM, 0)) != 0)
-		goto fail;
+	if (sc->txq_dynamic_cksum_toggle_supported == B_FALSE) {
+		if ((rc = sfxge_tx_qinit(sc, SFXGE_TXQ_NON_CKSUM,
+		    SFXGE_TXQ_NON_CKSUM, 0)) != 0)
+			goto fail;
 
-	if ((rc = sfxge_tx_qinit(sc, SFXGE_TXQ_IP_CKSUM,
-	    SFXGE_TXQ_IP_CKSUM, 0)) != 0)
-		goto fail2;
+		if ((rc = sfxge_tx_qinit(sc, SFXGE_TXQ_IP_CKSUM,
+		    SFXGE_TXQ_IP_CKSUM, 0)) != 0)
+			goto fail2;
+	}
 
 	for (index = 0;
 	     index < sc->txq_count - SFXGE_EVQ0_N_TXQ(sc) + 1;