gve: Correct ethtool rx_dropped calculation

The gve driver's "rx_dropped" statistic, exposed via `ethtool -S`,
incorrectly includes `rx_buf_alloc_fail` counts. These failures
represent an inability to allocate receive buffers, not true packet
drops where a received packet is discarded. This misrepresentation can
lead to inaccurate diagnostics.

This patch rectifies the ethtool "rx_dropped" calculation. It removes
`rx_buf_alloc_fail` from the total and adds `xdp_tx_errors` and
`xdp_redirect_errors`, which represent legitimate packet drops within
the XDP path.

Cc: [e-mail]
Fixes: 433e274b8f7b ("gve: Add stats for gve.")
Signed-off-by: Max Yuan <[e-mail]>
Reviewed-by: Jordan Rhee <[e-mail]>
Reviewed-by: Joshua Washington <[e-mail]>
Reviewed-by: Matt Olson <[e-mail]>
Signed-off-by: Harshitha Ramamurthy <[e-mail]>
Reviewed-by: Jacob Keller <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/ethernet/google/gve/gve_ethtool.c

···
 	u64 tmp_rx_pkts, tmp_rx_hsplit_pkt, tmp_rx_bytes, tmp_rx_hsplit_bytes,
 		tmp_rx_skb_alloc_fail, tmp_rx_buf_alloc_fail,
 		tmp_rx_desc_err_dropped_pkt, tmp_rx_hsplit_unsplit_pkt,
-		tmp_tx_pkts, tmp_tx_bytes;
+		tmp_tx_pkts, tmp_tx_bytes,
+		tmp_xdp_tx_errors, tmp_xdp_redirect_errors;
 	u64 rx_buf_alloc_fail, rx_desc_err_dropped_pkt, rx_hsplit_unsplit_pkt,
 		rx_pkts, rx_hsplit_pkt, rx_skb_alloc_fail, rx_bytes, tx_pkts, tx_bytes,
-		tx_dropped;
+		tx_dropped, xdp_tx_errors, xdp_redirect_errors;
 	int rx_base_stats_idx, max_rx_stats_idx, max_tx_stats_idx;
 	int stats_idx, stats_region_len, nic_stats_len;
 	struct stats *report_stats;
···
 	for (rx_pkts = 0, rx_bytes = 0, rx_hsplit_pkt = 0,
 	     rx_skb_alloc_fail = 0, rx_buf_alloc_fail = 0,
 	     rx_desc_err_dropped_pkt = 0, rx_hsplit_unsplit_pkt = 0,
+	     xdp_tx_errors = 0, xdp_redirect_errors = 0,
 	     ring = 0;
 	     ring < priv->rx_cfg.num_queues; ring++) {
 		if (priv->rx) {
···
 					rx->rx_desc_err_dropped_pkt;
 				tmp_rx_hsplit_unsplit_pkt =
 					rx->rx_hsplit_unsplit_pkt;
+				tmp_xdp_tx_errors = rx->xdp_tx_errors;
+				tmp_xdp_redirect_errors =
+					rx->xdp_redirect_errors;
 			} while (u64_stats_fetch_retry(&priv->rx[ring].statss,
 						       start));
 			rx_pkts += tmp_rx_pkts;
···
 			rx_buf_alloc_fail += tmp_rx_buf_alloc_fail;
 			rx_desc_err_dropped_pkt += tmp_rx_desc_err_dropped_pkt;
 			rx_hsplit_unsplit_pkt += tmp_rx_hsplit_unsplit_pkt;
+			xdp_tx_errors += tmp_xdp_tx_errors;
+			xdp_redirect_errors += tmp_xdp_redirect_errors;
 		}
 	}
 	for (tx_pkts = 0, tx_bytes = 0, tx_dropped = 0, ring = 0;
···
 	data[i++] = rx_bytes;
 	data[i++] = tx_bytes;
 	/* total rx dropped packets */
-	data[i++] = rx_skb_alloc_fail + rx_buf_alloc_fail +
-		    rx_desc_err_dropped_pkt;
+	data[i++] = rx_skb_alloc_fail + rx_desc_err_dropped_pkt +
+		    xdp_tx_errors + xdp_redirect_errors;
 	data[i++] = tx_dropped;
 	data[i++] = priv->tx_timeo_cnt;
 	data[i++] = rx_skb_alloc_fail;
···
 				tmp_rx_buf_alloc_fail = rx->rx_buf_alloc_fail;
 				tmp_rx_desc_err_dropped_pkt =
 					rx->rx_desc_err_dropped_pkt;
+				tmp_xdp_tx_errors = rx->xdp_tx_errors;
+				tmp_xdp_redirect_errors =
+					rx->xdp_redirect_errors;
 			} while (u64_stats_fetch_retry(&priv->rx[ring].statss,
 						       start));
 			data[i++] = tmp_rx_bytes;
···
 			data[i++] = rx->rx_frag_alloc_cnt;
 			/* rx dropped packets */
 			data[i++] = tmp_rx_skb_alloc_fail +
-				tmp_rx_buf_alloc_fail +
-				tmp_rx_desc_err_dropped_pkt;
+				    tmp_rx_desc_err_dropped_pkt +
+				    tmp_xdp_tx_errors +
+				    tmp_xdp_redirect_errors;
 			data[i++] = rx->rx_copybreak_pkt;
 			data[i++] = rx->rx_copied_pkt;
 			/* stats from NIC */