Index: head/sys/dev/sfxge/common/ef10_impl.h
===================================================================
--- head/sys/dev/sfxge/common/ef10_impl.h
+++ head/sys/dev/sfxge/common/ef10_impl.h
@@ -1193,6 +1193,22 @@
 	__in			efx_nic_t *enp,
 	__out			uint32_t *maskp);
 
+#if EFSYS_OPT_FW_SUBVARIANT_AWARE
+
+extern	__checkReturn	efx_rc_t
+efx_mcdi_get_nic_global(
+	__in		efx_nic_t *enp,
+	__in		uint32_t key,
+	__out		uint32_t *valuep);
+
+extern	__checkReturn	efx_rc_t
+efx_mcdi_set_nic_global(
+	__in		efx_nic_t *enp,
+	__in		uint32_t key,
+	__in		uint32_t value);
+
+#endif	/* EFSYS_OPT_FW_SUBVARIANT_AWARE */
+
 
 #if EFSYS_OPT_RX_PACKED_STREAM
 
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
@@ -2324,5 +2324,87 @@
 
 #endif	/* EFSYS_OPT_DIAG */
 
+#if EFSYS_OPT_FW_SUBVARIANT_AWARE
+
+	__checkReturn	efx_rc_t
+efx_mcdi_get_nic_global(
+	__in		efx_nic_t *enp,
+	__in		uint32_t key,
+	__out		uint32_t *valuep)
+{
+	efx_mcdi_req_t req;
+	uint8_t payload[MAX(MC_CMD_GET_NIC_GLOBAL_IN_LEN,
+			    MC_CMD_GET_NIC_GLOBAL_OUT_LEN)];
+	efx_rc_t rc;
+
+	(void) memset(payload, 0, sizeof (payload));
+	req.emr_cmd = MC_CMD_GET_NIC_GLOBAL;
+	req.emr_in_buf = payload;
+	req.emr_in_length = MC_CMD_GET_NIC_GLOBAL_IN_LEN;
+	req.emr_out_buf = payload;
+	req.emr_out_length = MC_CMD_GET_NIC_GLOBAL_OUT_LEN;
+
+	MCDI_IN_SET_DWORD(req, GET_NIC_GLOBAL_IN_KEY, key);
+
+	efx_mcdi_execute(enp, &req);
+
+	if (req.emr_rc != 0) {
+		rc = req.emr_rc;
+		goto fail1;
+	}
+
+	if (req.emr_out_length_used != MC_CMD_GET_NIC_GLOBAL_OUT_LEN) {
+		rc = EMSGSIZE;
+		goto fail2;
+	}
+
+	*valuep = MCDI_OUT_DWORD(req, GET_NIC_GLOBAL_OUT_VALUE);
+
+	return (0);
+
+fail2:
+	EFSYS_PROBE(fail2);
+fail1:
+	EFSYS_PROBE1(fail1, efx_rc_t, rc);
+
+	return (rc);
+}
+
+	__checkReturn	efx_rc_t
+efx_mcdi_set_nic_global(
+	__in		efx_nic_t *enp,
+	__in		uint32_t key,
+	__in		uint32_t value)
+{
+	efx_mcdi_req_t req;
+	uint8_t payload[MC_CMD_SET_NIC_GLOBAL_IN_LEN];
+	efx_rc_t rc;
+
+	(void) memset(payload, 0, sizeof (payload));
+	req.emr_cmd = MC_CMD_SET_NIC_GLOBAL;
+	req.emr_in_buf = payload;
+	req.emr_in_length = MC_CMD_SET_NIC_GLOBAL_IN_LEN;
+	req.emr_out_buf = NULL;
+	req.emr_out_length = 0;
+
+	MCDI_IN_SET_DWORD(req, SET_NIC_GLOBAL_IN_KEY, key);
+	MCDI_IN_SET_DWORD(req, SET_NIC_GLOBAL_IN_VALUE, value);
+
+	efx_mcdi_execute(enp, &req);
+
+	if (req.emr_rc != 0) {
+		rc = req.emr_rc;
+		goto fail1;
+	}
+
+	return (0);
+
+fail1:
+	EFSYS_PROBE1(fail1, efx_rc_t, rc);
+
+	return (rc);
+}
+
+#endif	/* EFSYS_OPT_FW_SUBVARIANT_AWARE */
 
 #endif	/* EFSYS_OPT_HUNTINGTON || EFSYS_OPT_MEDFORD || EFSYS_OPT_MEDFORD2 */
Index: head/sys/dev/sfxge/common/efx.h
===================================================================
--- head/sys/dev/sfxge/common/efx.h
+++ head/sys/dev/sfxge/common/efx.h
@@ -2891,6 +2891,38 @@
 
 #endif /* EFSYS_OPT_TUNNEL */
 
+#if EFSYS_OPT_FW_SUBVARIANT_AWARE
+
+/**
+ * Firmware subvariant choice options.
+ *
+ * It may be switched to no Tx checksum if attached drivers are either
+ * preboot or firmware subvariant aware and no VIS are allocated.
+ * If may be always switched to default explicitly using set request or
+ * implicitly if unaware driver is attaching. If switching is done when
+ * a driver is attached, it gets MC_REBOOT event and should recreate its
+ * datapath.
+ *
+ * See SF-119419-TC DPDK Firmware Driver Interface and
+ * SF-109306-TC EF10 for Driver Writers for details.
+ */
+typedef enum efx_nic_fw_subvariant_e {
+	EFX_NIC_FW_SUBVARIANT_DEFAULT = 0,
+	EFX_NIC_FW_SUBVARIANT_NO_TX_CSUM = 1,
+	EFX_NIC_FW_SUBVARIANT_NTYPES
+} efx_nic_fw_subvariant_t;
+
+extern	__checkReturn	efx_rc_t
+efx_nic_get_fw_subvariant(
+	__in		efx_nic_t *enp,
+	__out		efx_nic_fw_subvariant_t *subvariantp);
+
+extern	__checkReturn	efx_rc_t
+efx_nic_set_fw_subvariant(
+	__in		efx_nic_t *enp,
+	__in		efx_nic_fw_subvariant_t subvariant);
+
+#endif	/* EFSYS_OPT_FW_SUBVARIANT_AWARE */
 
 #ifdef	__cplusplus
 }
Index: head/sys/dev/sfxge/common/efx_nic.c
===================================================================
--- head/sys/dev/sfxge/common/efx_nic.c
+++ head/sys/dev/sfxge/common/efx_nic.c
@@ -976,6 +976,82 @@
 	return (rc);
 }
 
+#if EFSYS_OPT_FW_SUBVARIANT_AWARE
+
+	__checkReturn	efx_rc_t
+efx_nic_get_fw_subvariant(
+	__in		efx_nic_t *enp,
+	__out		efx_nic_fw_subvariant_t *subvariantp)
+{
+	efx_rc_t rc;
+	uint32_t value;
+
+	rc = efx_mcdi_get_nic_global(enp,
+	    MC_CMD_SET_NIC_GLOBAL_IN_FIRMWARE_SUBVARIANT, &value);
+	if (rc != 0)
+		goto fail1;
+
+	/* Mapping is not required since values match MCDI */
+	EFX_STATIC_ASSERT(EFX_NIC_FW_SUBVARIANT_DEFAULT ==
+	    MC_CMD_SET_NIC_GLOBAL_IN_FW_SUBVARIANT_DEFAULT);
+	EFX_STATIC_ASSERT(EFX_NIC_FW_SUBVARIANT_NO_TX_CSUM ==
+	    MC_CMD_SET_NIC_GLOBAL_IN_FW_SUBVARIANT_NO_TX_CSUM);
+
+	switch (value) {
+	case MC_CMD_SET_NIC_GLOBAL_IN_FW_SUBVARIANT_DEFAULT:
+	case MC_CMD_SET_NIC_GLOBAL_IN_FW_SUBVARIANT_NO_TX_CSUM:
+		*subvariantp = value;
+		break;
+	default:
+		rc = EINVAL;
+		goto fail2;
+	}
+
+	return (0);
+
+fail2:
+	EFSYS_PROBE(fail2);
+
+fail1:
+	EFSYS_PROBE1(fail1, efx_rc_t, rc);
+
+	return (rc);
+}
+
+	__checkReturn	efx_rc_t
+efx_nic_set_fw_subvariant(
+	__in		efx_nic_t *enp,
+	__in		efx_nic_fw_subvariant_t subvariant)
+{
+	efx_rc_t rc;
+
+	switch (subvariant) {
+	case EFX_NIC_FW_SUBVARIANT_DEFAULT:
+	case EFX_NIC_FW_SUBVARIANT_NO_TX_CSUM:
+		/* Mapping is not required since values match MCDI */
+		break;
+	default:
+		rc = EINVAL;
+		goto fail1;
+	}
+
+	rc = efx_mcdi_set_nic_global(enp,
+	    MC_CMD_SET_NIC_GLOBAL_IN_FIRMWARE_SUBVARIANT, subvariant);
+	if (rc != 0)
+		goto fail2;
+
+	return (0);
+
+fail2:
+	EFSYS_PROBE(fail2);
+
+fail1:
+	EFSYS_PROBE1(fail1, efx_rc_t, rc);
+
+	return (rc);
+}
+
+#endif	/* EFSYS_OPT_FW_SUBVARIANT_AWARE */
 
 	__checkReturn	efx_rc_t
 efx_nic_check_pcie_link_speed(