RE: [PATCH] net/mlx5: fix unbind of incorrect hairpin queue

[Raslan Darawsheh <rasland@nvidia.com>]

Hi,

> -----Original Message-----
> From: Dariusz Sosnowski <dsosnowski@nvidia.com>
> Sent: Thursday, November 9, 2023 8:01 PM
> To: Matan Azrad <matan@nvidia.com>; Slava Ovsiienko
> <viacheslavo@nvidia.com>; Ori Kam <orika@nvidia.com>; Suanming Mou
> <suanmingm@nvidia.com>; Bing Zhao <bingz@nvidia.com>
> Cc: dev@dpdk.org; Raslan Darawsheh <rasland@nvidia.com>;
> stable@dpdk.org
> Subject: [PATCH] net/mlx5: fix unbind of incorrect hairpin queue
> 
> Let's take an application with the following configuration:
> 
> - It uses 2 ports.
> - Each port has 3 Rx queues and 3 Tx queues.
> - On each port, Rx queues have a following purposes:
>   - Rx queue 0 - SW queue,
>   - Rx queue 1 - hairpin queue, bound to Tx queue on the same port,
>   - Rx queue 2 - hairpin queue, bound to Tx queue on another port.
> - On each port, Tx queues have a following purposes:
>   - Tx queue 0 - SW queue,
>   - Tx queue 1 - hairpin queue, bound to Rx queue on the same port,
>   - Tx queue 2 - hairpin queue, bound to Rx queue on another port.
> - Application configured all of the hairpin queues for manual binding.
> 
> After ports are configured and queues are set up, if the application does the
> following API call sequence:
> 
> 1. rte_eth_dev_start(port_id=0)
> 2. rte_eth_hairpin_bind(tx_port=0, rx_port=0) 3.
> rte_eth_hairpin_bind(tx_port=0, rx_port=1)
> 
> mlx5 PMD fails to modify SQ and logs this error:
> 
>   mlx5_common: mlx5_devx_cmds.c:2079: mlx5_devx_cmd_modify_sq():
>     Failed to modify SQ using DevX
> 
> This error was caused by an incorrect unbind operation taken during error
> handling inside call (3).
> 
> (3) fails, because port 1 (Rx side of the hairpin) was not started.
> As a result of this failure, PMD goes into error handling, where all previously
> bound hairpin queues are unbound.
> This is incorrect, since this error handling procedure in rte_eth_hairpin_bind()
> implementation assumes that all hairpin queues are bound to the same
> rx_port, which is not the case.
> The following sequence of function calls appears:
> 
> - rte_eth_hairpin_queue_peer_unbind(rx_port=**1**, rx_queue=1, 0),
> - mlx5_hairpin_queue_peer_unbind(dev=**port 0**, tx_queue=1, 1).
> 
> Which violates the hairpin queue destroy flow, by unbinding Tx queue 1 on
> port 0, before unbinding Rx queue 1 on port 1.
> 
> This patch fixes that behavior, by filtering Tx queues on which error handling is
> done to only affect:
> 
> - hairpin queues (it also reduces unnecessary debug log messages),
> - hairpin queues connected to the rx_port which is currently processed.
> 
> Fixes: 37cd4501e873 ("net/mlx5: support two ports hairpin mode")
> Cc: bingz@nvidia.com
> Cc: stable@dpdk.org
> 
> Signed-off-by: Dariusz Sosnowski <dsosnowski@nvidia.com>
> Acked-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>
> ---

Patch applied to next-net-mlx,

Kindest regards,
Raslan Darawsheh