sfc: support GRE TSO on EF100

We can treat SKB_GSO_GRE almost exactly the same as UDP tunnels, except
 that we don't want to edit the outer UDP len (as there isn't one).
For SKB_GSO_GRE_CSUM, we have to use GSO_PARTIAL as the device doesn't
 support offload of non-UDP outer L4 checksums.
Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Acked-by: Martin Habets <mhabets@solarflare.com>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>

drivers/net/ethernet/sfc/ef100_nic.c

@@ -185,11 +185,16 @@ static int efx_ef100_init_datapath_caps(struct efx_nic *efx)
 	if (efx_ef100_has_cap(nic_data->datapath_caps2, TX_TSO_V3)) {
 		struct net_device *net_dev = efx->net_dev;
 		netdev_features_t tso = NETIF_F_TSO | NETIF_F_TSO6 | NETIF_F_GSO_PARTIAL |
-					NETIF_F_GSO_UDP_TUNNEL | NETIF_F_GSO_UDP_TUNNEL_CSUM;
+					NETIF_F_GSO_UDP_TUNNEL | NETIF_F_GSO_UDP_TUNNEL_CSUM |
+					NETIF_F_GSO_GRE | NETIF_F_GSO_GRE_CSUM;
 
 		net_dev->features |= tso;
 		net_dev->hw_features |= tso;
 		net_dev->hw_enc_features |= tso;
+		/* EF100 HW can only offload outer checksums if they are UDP,
+		 * so for GRE_CSUM we have to use GSO_PARTIAL.
+		 */
+		net_dev->gso_partial_features |= NETIF_F_GSO_GRE_CSUM;
 	}
 	efx->num_mac_stats = MCDI_WORD(outbuf,
 				       GET_CAPABILITIES_V4_OUT_MAC_STATS_NUM_STATS);

drivers/net/ethernet/sfc/ef100_tx.c

@@ -194,6 +194,7 @@ static void ef100_make_tso_desc(struct efx_nic *efx,
 	u16 vlan_tci = skb_vlan_tag_get(skb);
 	u32 mss = skb_shinfo(skb)->gso_size;
 	bool encap = skb->encapsulation;
+	bool udp_encap = false;
 	u16 vlan_enable = 0;
 	struct tcphdr *tcp;
 	bool outer_csum;
@@ -212,6 +213,9 @@ static void ef100_make_tso_desc(struct efx_nic *efx,
 		outer_l4_offset = skb_transport_offset(skb);
 		ip_offset = skb_inner_network_offset(skb);
 		tcp_offset = skb_inner_transport_offset(skb);
+		if (skb_shinfo(skb)->gso_type &
+		    (SKB_GSO_UDP_TUNNEL | SKB_GSO_UDP_TUNNEL_CSUM))
+			udp_encap = true;
 	} else {
 		ip_offset =  skb_network_offset(skb);
 		tcp_offset = skb_transport_offset(skb);
@@ -239,7 +243,7 @@ static void ef100_make_tso_desc(struct efx_nic *efx,
 			      ESF_GZ_TX_TSO_ED_INNER_IP_LEN, 1,
 			      ESF_GZ_TX_TSO_OUTER_L3_OFF_W, outer_ip_offset >> 1,
 			      ESF_GZ_TX_TSO_OUTER_L4_OFF_W, outer_l4_offset >> 1,
-			      ESF_GZ_TX_TSO_ED_OUTER_UDP_LEN, encap && !gso_partial,
+			      ESF_GZ_TX_TSO_ED_OUTER_UDP_LEN, udp_encap && !gso_partial,
 			      ESF_GZ_TX_TSO_ED_OUTER_IP_LEN, encap && !gso_partial,
 			      ESF_GZ_TX_TSO_ED_OUTER_IP4_ID, encap ? mangleid :
 								     ESE_GZ_TX_DESC_IP4_ID_NO_OP,