[PATCH v3 6/7] net/mlx5: fix fast-path ops setup in secondary process

[longli@linux.microsoft.com]

From: Long Li <longli@microsoft.com>

On hotplug, the secondary process is not able to set rte_eth_fp_ops
because the primary process has not finished setting up the device
for datapath.

When the primary process re-attaches a VF during a hot-add event
(e.g. Accelerated Networking re-enabled on Azure), it sends
MLX5_MP_REQ_START_RXTX to the secondary process. The secondary
handler sets rx/tx burst functions and reinitializes UAR mappings,
but does not update the fast-path queue data pointers. The stale
rxq.data and txq.data in rte_eth_fp_ops cause a segfault when the
secondary resumes polling the re-added VF port.

Fix this by setting rte_eth_fp_ops rxq.data and txq.data to point
to the device's RX/TX queue arrays in the secondary process when
the primary requests to start datapath, before the memory barrier.

Also update rte_eth_fp_ops burst function pointers in the STOP_RXTX
handler. Without this, the secondary's rte_eth_fp_ops retains stale
burst function pointers after stop, since rte_eth_fp_ops is
process-local and eth_dev_fp_ops_reset() in rte_eth_dev_stop() only
affects the primary.

Without this fix, the secondary process crashes with SIGSEGV in
rte_eth_rx_burst() at qd = p->rxq.data[queue_id] when the VF is
hot-added back.

Fixes: 2aac5b5d119f ("net/mlx5: sync stop/start with secondary process")
Cc: stable@dpdk.org

Signed-off-by: Long Li <longli@microsoft.com>
---
 drivers/net/mlx5/linux/mlx5_mp_os.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/mlx5/linux/mlx5_mp_os.c b/drivers/net/mlx5/linux/mlx5_mp_os.c
index f2e71c9bd4..955a990a39 100644
--- a/drivers/net/mlx5/linux/mlx5_mp_os.c
+++ b/drivers/net/mlx5/linux/mlx5_mp_os.c
@@ -189,6 +189,8 @@ struct rte_mp_msg mp_res;
 			}
 		}
 		close(mp_msg->fds[0]);
+		rte_eth_fp_ops[param->port_id].rxq.data = dev->data->rx_queues;
+		rte_eth_fp_ops[param->port_id].txq.data = dev->data->tx_queues;
 		rte_mb();
 		mp_init_msg(&priv->mp_id, &mp_res, param->type);
 		res->result = 0;
@@ -198,6 +200,8 @@ struct rte_mp_msg mp_res;
 		DRV_LOG(INFO, "port %u stopping datapath", dev->data->port_id);
 		dev->rx_pkt_burst = rte_eth_pkt_burst_dummy;
 		dev->tx_pkt_burst = rte_eth_pkt_burst_dummy;
+		rte_eth_fp_ops[param->port_id].rx_pkt_burst = rte_eth_pkt_burst_dummy;
+		rte_eth_fp_ops[param->port_id].tx_pkt_burst = rte_eth_pkt_burst_dummy;
 		rte_mb();
 		mp_init_msg(&priv->mp_id, &mp_res, param->type);
 		res->result = 0;
-- 
2.43.0