Commit c8591dec authored by Tariq Toukan's avatar Tariq Toukan Committed by Paolo Abeni
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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: 3b88a535 ("net/mlx5e: Defer channels closure to reduce interface down time")
Signed-off-by: default avatarTariq Toukan <tariqt@nvidia.com>
Signed-off-by: default avatarWilliam Tu <witu@nvidia.com>
Reviewed-by: default avatarDragos Tatulea <dtatulea@nvidia.com>
Link: https://patch.msgid.link/1765284977-1363052-9-git-send-email-tariqt@nvidia.com


Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent 9ab89bde

drivers/net/ethernet/mellanox/mlx5/core/en_tx.c

+5 −1
Original line number Diff line number Diff line
@@ -939,6 +939,10 @@ void mlx5e_free_txqsq_descs(struct mlx5e_txqsq *sq) 
	sq->dma_fifo_cc = dma_fifo_cc;

	sq->cc = sqcc;



	/* 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);

}