Commit 958b3d39 authored Oct 13, 2016 by Brenden Blanco Committed by David S. Miller Oct 14, 2016

net/mlx4_en: fixup xdp tx irq to match rx

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: 9ecc2d86 ("net/mlx4_en: add xdp forwarding and data write support")
Reported-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent fbbfa34c

drivers/net/ethernet/mellanox/mlx4/en_cq.c

+9 −1

Original line number	Diff line number	Diff line
		@@ -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;