From c8591decd9dbf395cb8ae398e70b0438fdd24aee Mon Sep 17 00:00:00 2001 From: Tariq Toukan Date: Tue, 9 Dec 2025 14:56:16 +0200 Subject: [PATCH] net/mlx5e: Do not update BQL of old txqs during channel reconfiguration During channel reconfiguration (e.g., ethtool private flags changes), the driver can trigger a kernel BUG_ON in dql_completed() with the error "kernel BUG at lib/dynamic_queue_limits.c:99". The issue occurs in the following sequence: During mlx5e_safe_switch_params(), old channels are deactivated via mlx5e_deactivate_txqsq(). New channels are created and activated, taking ownership of the netdev_queues and their BQL state. When old channels are closed via mlx5e_close_txqsq(), there may be pending TX descriptors (sq->cc != sq->pc) that were in-flight during the deactivation. mlx5e_free_txqsq_descs() frees these pending descriptors and attempts to complete them via netdev_tx_completed_queue(). However, the BQL state (dql->num_queued and dql->num_completed) have been reset in mlx5e_activate_txqsq and belong to the new queue owner, leading to dql->num_queued - dql->num_completed < nbytes. This triggers BUG_ON(count > num_queued - num_completed) in dql_completed(). Fixes: 3b88a535a8e1 ("net/mlx5e: Defer channels closure to reduce interface down time") Signed-off-by: Tariq Toukan Signed-off-by: William Tu Reviewed-by: Dragos Tatulea Link: https://patch.msgid.link/1765284977-1363052-9-git-send-email-tariqt@nvidia.com Signed-off-by: Paolo Abeni --- drivers/net/ethernet/mellanox/mlx5/core/en_tx.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c index 14884b9ea7f3..a01ee656a1e7 100644 --- a/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c @@ -939,7 +939,11 @@ void mlx5e_free_txqsq_descs(struct mlx5e_txqsq *sq) sq->dma_fifo_cc = dma_fifo_cc; sq->cc = sqcc; - netdev_tx_completed_queue(sq->txq, npkts, nbytes); + /* Do not update BQL for TXQs that got replaced by new active ones, as + * netdev_tx_reset_queue() is called for them in mlx5e_activate_txqsq(). + */ + if (sq == sq->priv->txq2sq[sq->txq_ix]) + netdev_tx_completed_queue(sq->txq, npkts, nbytes); } #ifdef CONFIG_MLX5_CORE_IPOIB -- 2.47.3