[PATCH net 2/2] gve: Correct ethtool rx_dropped calculation

[Harshitha Ramamurthy <hramamurthy@google.com>]

From: Max Yuan <maxyuan@google.com>

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: stable@vger.kernel.org
Fixes: 433e274b8f7b ("gve: Add stats for gve.")
Signed-off-by: Max Yuan <maxyuan@google.com>
Reviewed-by: Jordan Rhee <jordanrhee@google.com>
Reviewed-by: Joshua Washington <joshwash@google.com>
Reviewed-by: Matt Olson <maolson@google.com>
Signed-off-by: Harshitha Ramamurthy <hramamurthy@google.com>
---
 drivers/net/ethernet/google/gve/gve_ethtool.c | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/google/gve/gve_ethtool.c b/drivers/net/ethernet/google/gve/gve_ethtool.c
index f7864ae7..9fd954d1 100644
--- a/drivers/net/ethernet/google/gve/gve_ethtool.c
+++ b/drivers/net/ethernet/google/gve/gve_ethtool.c
@@ -152,10 +152,11 @@ gve_get_ethtool_stats(struct net_device *netdev,
 	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;
@@ -199,6 +200,7 @@ gve_get_ethtool_stats(struct net_device *netdev,
 	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) {
@@ -216,6 +218,9 @@ gve_get_ethtool_stats(struct net_device *netdev,
 					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;
@@ -225,6 +230,8 @@ gve_get_ethtool_stats(struct net_device *netdev,
 			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;
@@ -250,8 +257,8 @@ gve_get_ethtool_stats(struct net_device *netdev,
 	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;
@@ -330,6 +337,9 @@ gve_get_ethtool_stats(struct net_device *netdev,
 				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;
@@ -340,8 +350,9 @@ gve_get_ethtool_stats(struct net_device *netdev,
 			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 */
-- 
2.53.0.rc1.225.gd81095ad13-goog