In cases where the number of tx rings is not a multiple of the number of
rx rings, the tx completion event will be handled on a different core
from the transmit and population of the ring. Races on the ring will
lead to a double-free of the page, and possibly other corruption.
The rings are initialized by default with a valid multiple of rings,
based on the number of cpus, therefore an invalid configuration requires
ethtool to change the ring layout. For instance 'ethtool -L eth0 rx 9 tx
8' will cause packets received on rx0, and XDP_TX'd to tx48, to be
completed on cpu3 (48 % 9 == 3).
Resolve this discrepancy by shifting the irq for the xdp tx queues to
start again from 0, modulo rx_ring_num.
Fixes: 9ecc2d86171a ("net/mlx4_en: add xdp forwarding and data write support")
Reported-by: Jesper Dangaard Brouer <bro...@redhat.com>
Signed-off-by: Brenden Blanco <bbla...@plumgrid.com>
---
drivers/net/ethernet/mellanox/mlx4/en_cq.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/drivers/net/ethernet/mellanox/mlx4/en_cq.c
b/drivers/net/ethernet/mellanox/mlx4/en_cq.c
index 132cea6..e3be7e4 100644
--- a/drivers/net/ethernet/mellanox/mlx4/en_cq.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_cq.c
@@ -127,7 +127,15 @@ int mlx4_en_activate_cq(struct mlx4_en_priv *priv, struct
mlx4_en_cq *cq,
/* For TX we use the same irq per
ring we assigned for the RX */
struct mlx4_en_cq *rx_cq;
-
+ int xdp_index;
+
+ /* The xdp tx irq must align with the rx ring that forwards to
+ * it, so reindex these from 0. This should only happen when
+ * tx_ring_num is not a multiple of rx_ring_num.
+ */
+ xdp_index = (priv->xdp_ring_num - priv->tx_ring_num) + cq_idx;
+ if (xdp_index >= 0)
+ cq_idx = xdp_index;
cq_idx = cq_idx % priv->rx_ring_num;
rx_cq = priv->rx_cq[cq_idx];
cq->vector = rx_cq->vector;
--
2.9.3
