ice, xsk: Decorate ICE_XDP_REDIR with likely()

ice_run_xdp_zc() suggests to compiler that XDP_REDIRECT is the most
probable action returned from BPF program that AF_XDP has in its
pipeline. Let's also bring this suggestion up to the callsite of
ice_run_xdp_zc() so that compiler will be able to generate more
optimized code which in turn will make branch predictor happy.
Suggested-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220413153015.453864-4-maciej.fijalkowski@intel.com

drivers/net/ethernet/intel/ice/ice_xsk.c

@@ -629,18 +629,19 @@ int ice_clean_rx_irq_zc(struct ice_rx_ring *rx_ring, int budget)
 		xsk_buff_dma_sync_for_cpu(xdp, rx_ring->xsk_pool);
 
 		xdp_res = ice_run_xdp_zc(rx_ring, xdp, xdp_prog, xdp_ring);
-		if (xdp_res) {
-			if (xdp_res & (ICE_XDP_TX | ICE_XDP_REDIR))
-				xdp_xmit |= xdp_res;
-			else
-				xsk_buff_free(xdp);
+		if (likely(xdp_res & (ICE_XDP_TX | ICE_XDP_REDIR)))
+			xdp_xmit |= xdp_res;
+		else if (xdp_res == ICE_XDP_CONSUMED)
+			xsk_buff_free(xdp);
+		else
+			goto construct_skb;
 
-			total_rx_bytes += size;
-			total_rx_packets++;
+		total_rx_bytes += size;
+		total_rx_packets++;
+
+		ice_bump_ntc(rx_ring);
+		continue;
 
-			ice_bump_ntc(rx_ring);
-			continue;
-		}
 construct_skb:
 		/* XDP_PASS path */
 		skb = ice_construct_skb_zc(rx_ring, xdp);