6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: David Thompson davthompson@nvidia.com
[ Upstream commit dcea1bd45e6d111cc8fc1aaefa7e31694089bda3 ]
Under heavy traffic, the BlueField Gigabit interface can become unresponsive. This is due to a possible race condition in the mlxbf_gige_rx_packet function, where the function exits with producer and consumer indices equal but there are remaining packet(s) to be processed. In order to prevent this situation, read receive consumer index *before* the HW replenish so that the mlxbf_gige_rx_packet function returns an accurate return value even if a packet is received into just-replenished buffer prior to exiting this routine. If the just-replenished buffer is received and occupies the last RX ring entry, the interface would not recover and instead would encounter RX packet drops related to internal buffer shortages since the driver RX logic is not being triggered to drain the RX ring. This patch will address and prevent this "ring full" condition.
Fixes: f92e1869d74e ("Add Mellanox BlueField Gigabit Ethernet driver") Reviewed-by: Asmaa Mnebhi asmaa@nvidia.com Signed-off-by: David Thompson davthompson@nvidia.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_rx.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_rx.c b/drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_rx.c index 0d5a41a2ae010..227d01cace3f0 100644 --- a/drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_rx.c +++ b/drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_rx.c @@ -267,6 +267,13 @@ static bool mlxbf_gige_rx_packet(struct mlxbf_gige *priv, int *rx_pkts) priv->stats.rx_truncate_errors++; }
+ /* Read receive consumer index before replenish so that this routine + * returns accurate return value even if packet is received into + * just-replenished buffer prior to exiting this routine. + */ + rx_ci = readq(priv->base + MLXBF_GIGE_RX_CQE_PACKET_CI); + rx_ci_rem = rx_ci % priv->rx_q_entries; + /* Let hardware know we've replenished one buffer */ rx_pi++;
@@ -279,8 +286,6 @@ static bool mlxbf_gige_rx_packet(struct mlxbf_gige *priv, int *rx_pkts) rx_pi_rem = rx_pi % priv->rx_q_entries; if (rx_pi_rem == 0) priv->valid_polarity ^= 1; - rx_ci = readq(priv->base + MLXBF_GIGE_RX_CQE_PACKET_CI); - rx_ci_rem = rx_ci % priv->rx_q_entries;
if (skb) netif_receive_skb(skb);