Index: sys/dev/sfxge/common/ef10_nic.c
===================================================================
--- sys/dev/sfxge/common/ef10_nic.c
+++ sys/dev/sfxge/common/ef10_nic.c
@@ -1023,7 +1023,7 @@
 	efx_nic_cfg_t *encp = &(enp->en_nic_cfg);
 	efx_mcdi_req_t req;
 	uint8_t payload[MAX(MC_CMD_GET_CAPABILITIES_IN_LEN,
-			    MC_CMD_GET_CAPABILITIES_V2_OUT_LEN)];
+			    MC_CMD_GET_CAPABILITIES_V4_OUT_LEN)];
 	efx_rc_t rc;
 
 	if ((rc = ef10_mcdi_get_pf_count(enp, &encp->enc_hw_pf_count)) != 0)
@@ -1035,7 +1035,7 @@
 	req.emr_in_buf = payload;
 	req.emr_in_length = MC_CMD_GET_CAPABILITIES_IN_LEN;
 	req.emr_out_buf = payload;
-	req.emr_out_length = MC_CMD_GET_CAPABILITIES_V2_OUT_LEN;
+	req.emr_out_length = MC_CMD_GET_CAPABILITIES_V4_OUT_LEN;
 
 	efx_mcdi_execute_quiet(enp, &req);
 
@@ -1202,6 +1202,16 @@
 		encp->enc_tunnel_config_udp_entries_max = 0;
 	}
 
+	/* Check if firmware supports extended MAC stats. */
+	if (req.emr_out_length_used >= MC_CMD_GET_CAPABILITIES_V4_OUT_LEN) {
+		/* Extended stats buffer supported */
+		encp->enc_mac_stats_nstats = MCDI_OUT_WORD(req,
+		    GET_CAPABILITIES_V4_OUT_MAC_STATS_NUM_STATS);
+	} else {
+		/* Use Siena-compatible legacy MAC stats */
+		encp->enc_mac_stats_nstats = MC_CMD_MAC_NSTATS;
+	}
+
 #undef CAP_FLAGS1
 #undef CAP_FLAGS2
 
Index: sys/dev/sfxge/common/efx.h
===================================================================
--- sys/dev/sfxge/common/efx.h
+++ sys/dev/sfxge/common/efx.h
@@ -1260,6 +1260,8 @@
 	uint32_t		enc_max_pcie_link_gen;
 	/* Firmware verifies integrity of NVRAM updates */
 	uint32_t		enc_nvram_update_verify_result_supported;
+	/* Firmware support for extended MAC_STATS buffer */
+	uint32_t		enc_mac_stats_nstats;
 } efx_nic_cfg_t;
 
 #define	EFX_PCI_FUNCTION_IS_PF(_encp)	((_encp)->enc_vf == 0xffff)
Index: sys/dev/sfxge/common/siena_nic.c
===================================================================
--- sys/dev/sfxge/common/siena_nic.c
+++ sys/dev/sfxge/common/siena_nic.c
@@ -185,6 +185,8 @@
 
 	encp->enc_nvram_update_verify_result_supported = B_FALSE;
 
+	encp->enc_mac_stats_nstats = MC_CMD_MAC_NSTATS;
+
 	return (0);
 
 fail2: