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net/mlx5e: fix BQL reset on SQ re-activation

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mlx5e_queue_start() deactivates and re-activates all channels but closes
only the queue being restarted. mlx5e_activate_txqsq() then
unconditionally calls netdev_tx_reset_queue(), zeroing the BQL counters
of channels that kept their in-flight TX WQEs. The next completion then
over-charges and trips the BUG_ON() in dql_completed():

  kernel BUG at lib/dynamic_queue_limits.c:99!
  RIP: 0010:dql_completed+0x23d/0x280
  Call Trace:
   <IRQ>
   mlx5e_poll_tx_cq+0x668/0xa60
   mlx5e_napi_poll+0x5b/0x7b0
   net_rx_action+0x15a/0x580

Reset BQL only when the SQ has no bytes in flight (sq->cc == sq->pc).

In the case that reset is skipped, the outstanding WQEs will eventually
complete and rebalance the dql. The dql->limit is carried across the
reset.

Fixes: b2588ea40e ("net/mlx5e: Implement queue mgmt ops and single channel swap")
Signed-off-by: Bobby Eshleman <bobbyeshleman@meta.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/20260803-mlx5-bql-v3-1-a30d4c66fe1d@meta.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Bobby Eshleman 2026-08-03 16:47:29 -07:00 committed by Jakub Kicinski
parent 5d1c224dd9
commit e7386770be
1 changed files with 3 additions and 1 deletions
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4
drivers/net/ethernet/mellanox/mlx5/core/en_main.c
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@ -1939,8 +1939,10 @@ int mlx5e_open_txqsq(struct mlx5e_channel *c, u32 tisn, int txq_ix,
void mlx5e_activate_txqsq(struct mlx5e_txqsq *sq)
{
sq->txq = netdev_get_tx_queue(sq->netdev, sq->txq_ix);
/* Reset BQL only when the SQ has no bytes in flight. */
if (sq->cc == sq->pc)
netdev_tx_reset_queue(sq->txq);
set_bit(MLX5E_SQ_STATE_ENABLED, &sq->state);
netdev_tx_reset_queue(sq->txq);
netif_tx_start_queue(sq->txq);
netif_queue_set_napi(sq->netdev, sq->txq_ix, NETDEV_QUEUE_TYPE_TX, sq->cq.napi);
}