Index: head/sys/dev/sfxge/common/ef10_nic.c
===================================================================
--- head/sys/dev/sfxge/common/ef10_nic.c
+++ head/sys/dev/sfxge/common/ef10_nic.c
@@ -497,7 +497,8 @@
 efx_mcdi_get_capabilities(
 	__in		efx_nic_t *enp,
 	__out		uint32_t *flagsp,
-	__out		uint32_t *flags2p)
+	__out		uint32_t *flags2p,
+	__out		uint32_t *tso2ncp)
 {
 	efx_mcdi_req_t req;
 	uint8_t payload[MAX(MC_CMD_GET_CAPABILITIES_IN_LEN,
@@ -525,10 +526,14 @@
 
 	*flagsp = MCDI_OUT_DWORD(req, GET_CAPABILITIES_OUT_FLAGS1);
 
-	if (req.emr_out_length_used < MC_CMD_GET_CAPABILITIES_V2_OUT_LEN)
+	if (req.emr_out_length_used < MC_CMD_GET_CAPABILITIES_V2_OUT_LEN) {
 		*flags2p = 0;
-	else
+		*tso2ncp = 0;
+	} else {
 		*flags2p = MCDI_OUT_DWORD(req, GET_CAPABILITIES_V2_OUT_FLAGS2);
+		*tso2ncp = MCDI_OUT_WORD(req,
+				GET_CAPABILITIES_V2_OUT_TX_TSO_V2_N_CONTEXTS);
+	}
 
 	return (0);
 
@@ -963,9 +968,11 @@
 	efx_nic_cfg_t *encp = &(enp->en_nic_cfg);
 	uint32_t flags;
 	uint32_t flags2;
+	uint32_t tso2nc;
 	efx_rc_t rc;
 
-	if ((rc = efx_mcdi_get_capabilities(enp, &flags, &flags2)) != 0)
+	if ((rc = efx_mcdi_get_capabilities(enp, &flags, &flags2,
+					    &tso2nc)) != 0)
 		goto fail1;
 
 #define	CAP_FLAG(flags1, field)		\
@@ -992,6 +999,10 @@
 	encp->enc_fw_assisted_tso_v2_enabled =
 	    CAP_FLAG2(flags2, TX_TSO_V2) ? B_TRUE : B_FALSE;
 
+	/* Get the number of TSO contexts (FATSOv2) */
+	encp->enc_fw_assisted_tso_v2_n_contexts =
+		CAP_FLAG2(flags2, TX_TSO_V2) ? tso2nc : 0;
+
 	/* Check if the firmware has vadapter/vport/vswitch support */
 	encp->enc_datapath_cap_evb =
 	    CAP_FLAG(flags, EVB) ? B_TRUE : B_FALSE;
Index: head/sys/dev/sfxge/common/efx.h
===================================================================
--- head/sys/dev/sfxge/common/efx.h
+++ head/sys/dev/sfxge/common/efx.h
@@ -1139,6 +1139,8 @@
 	uint32_t		enc_tx_tso_tcp_header_offset_limit;
 	boolean_t		enc_fw_assisted_tso_enabled;
 	boolean_t		enc_fw_assisted_tso_v2_enabled;
+	/* Number of TSO contexts on the NIC (FATSOv2) */
+	uint32_t		enc_fw_assisted_tso_v2_n_contexts;
 	boolean_t		enc_hw_tx_insert_vlan_enabled;
 	/* Datapath firmware vadapter/vport/vswitch support */
 	boolean_t		enc_datapath_cap_evb;
Index: head/sys/dev/sfxge/common/siena_nic.c
===================================================================
--- head/sys/dev/sfxge/common/siena_nic.c
+++ head/sys/dev/sfxge/common/siena_nic.c
@@ -152,6 +152,7 @@
 	encp->enc_hw_tx_insert_vlan_enabled = B_FALSE;
 	encp->enc_fw_assisted_tso_enabled = B_FALSE;
 	encp->enc_fw_assisted_tso_v2_enabled = B_FALSE;
+	encp->enc_fw_assisted_tso_v2_n_contexts = 0;
 	encp->enc_allow_set_mac_with_installed_filters = B_TRUE;
 
 	/* Siena supports two 10G ports, and 8 lanes of PCIe Gen2 */