[PATCH net-next] net: stmmac: improve TSO/GSO queue selection

[Lorenzo Bianconi]

GSO (TSO/USO) frames are currently always sent through queue 0 since
the driver assumed there was no way to determine which queues are TSO
capable. This unconditionally pins all GSO traffic to queue 0, bypassing
the per-flow queue distribution and any XPS setup.

Instead, pick the queue through netdev_pick_tx() and only fall back to
queue 0 when the selected queue cannot run TSO, i.e. when TBS is enabled
on it, since TSO and TBS cannot coexist on the same channel (see
stmmac_tso_channel_permitted()).

While at it, base the check on priv->gso_enabled_types rather than a
hardcoded GSO type mask, so it matches the TSO/USO capability actually
used by the transmit path (e.g. UDP segmentation is only offloaded on
GMAC4).

Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi at oss.qualcomm.com>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index b2b7d0242dd3..99fc7313f247 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -6445,19 +6445,18 @@ static int stmmac_setup_tc(struct net_device *ndev, enum tc_setup_type type,
 static u16 stmmac_select_queue(struct net_device *dev, struct sk_buff *skb,
 			       struct net_device *sb_dev)
 {
-	int gso = skb_shinfo(skb)->gso_type;
+	u32 queue = netdev_pick_tx(dev, skb, NULL) % dev->real_num_tx_queues;
+	struct stmmac_priv *priv = netdev_priv(dev);
 
-	if (gso & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6 | SKB_GSO_UDP_L4)) {
-		/*
-		 * There is no way to determine the number of TSO/USO
-		 * capable Queues. Let's use always the Queue 0
-		 * because if TSO/USO is supported then at least this
-		 * one will be capable.
+	if ((skb_shinfo(skb)->gso_type & priv->gso_enabled_types) &&
+	    !stmmac_tso_channel_permitted(priv, queue)) {
+		/* GSO frames need HW TSO/USO, which cannot run on TBS queues.
+		 * Fall back to the queue reserved for TSO (queue 0).
 		 */
 		return 0;
 	}
 
-	return netdev_pick_tx(dev, skb, NULL) % dev->real_num_tx_queues;
+	return queue;
 }
 
 static int stmmac_set_mac_address(struct net_device *ndev, void *addr)

---
base-commit: 4fa4977a0d900f936bcae5cd2c510be5554e8dd6
change-id: 20260807-stmmac_select_queue-tso-fix-06cc586d4022

Best regards,
-- 
Lorenzo Bianconi <lorenzo.bianconi at oss.qualcomm.com>