nfp: move repr handling on RX path

Representor packets are received on PF queues with special metadata tag
for demux.  There is no reason to resolve the representor ID -> netdev
after the skb has been allocated.  Move the code, this will allow us to
handle special FW messages without SKB allocation overhead.
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Dirk van der Merwe <dirk.vandermerwe@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

drivers/net/ethernet/netronome/nfp/nfp_net_common.c

@@ -1757,6 +1757,21 @@ static int nfp_net_rx(struct nfp_net_rx_ring *rx_ring, int budget)
 			}
 		}
 
+		if (likely(!meta.portid)) {
+			netdev = dp->netdev;
+		} else {
+			struct nfp_net *nn;
+
+			nn = netdev_priv(dp->netdev);
+			netdev = nfp_app_repr_get(nn->app, meta.portid);
+			if (unlikely(!netdev)) {
+				nfp_net_rx_drop(dp, r_vec, rx_ring, rxbuf,
+						NULL);
+				continue;
+			}
+			nfp_repr_inc_rx_stats(netdev, pkt_len);
+		}
+
 		skb = build_skb(rxbuf->frag, true_bufsz);
 		if (unlikely(!skb)) {
 			nfp_net_rx_drop(dp, r_vec, rx_ring, rxbuf, NULL);
@@ -1772,20 +1787,6 @@ static int nfp_net_rx(struct nfp_net_rx_ring *rx_ring, int budget)
 
 		nfp_net_rx_give_one(dp, rx_ring, new_frag, new_dma_addr);
 
-		if (likely(!meta.portid)) {
-			netdev = dp->netdev;
-		} else {
-			struct nfp_net *nn;
-
-			nn = netdev_priv(dp->netdev);
-			netdev = nfp_app_repr_get(nn->app, meta.portid);
-			if (unlikely(!netdev)) {
-				nfp_net_rx_drop(dp, r_vec, rx_ring, NULL, skb);
-				continue;
-			}
-			nfp_repr_inc_rx_stats(netdev, pkt_len);
-		}
-
 		skb_reserve(skb, pkt_off);
 		skb_put(skb, pkt_len);