NACK: [SRU][FOCAL][PATCH 1/1] net/mlx5: Fix a race when moving command interface to polling mode

[William Breathitt Gray]

On Tue, Jan 19, 2021 at 11:00:15AM -0500, William Breathitt Gray wrote:
> From: Eran Ben Elisha <eranbe at mellanox.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1905574
> 
> As part of driver unload, it destroys the commands EQ (via FW command).
> As the commands EQ is destroyed, FW will not generate EQEs for any command
> that driver sends afterwards. Driver should poll for later commands status.
> 
> Driver commands mode metadata is updated before the commands EQ is
> actually destroyed. This can lead for double completion handle by the
> driver (polling and interrupt), if a command is executed and completed by
> FW after the mode was changed, but before the EQ was destroyed.
> 
> Fix that by using the mlx5_cmd_allowed_opcode mechanism to guarantee
> that only DESTROY_EQ command can be executed during this time period.
> 
> Fixes: e126ba97dba9 ("mlx5: Add driver for Mellanox Connect-IB adapters")
> Signed-off-by: Eran Ben Elisha <eranbe at mellanox.com>
> Reviewed-by: Moshe Shemesh <moshe at mellanox.com>
> Signed-off-by: Saeed Mahameed <saeedm at nvidia.com>
> (cherry-picked from commit 432161ea26d6d5e5c3f7306d9407d26ed1e1953e)

Cherry pick line has a typo.

Nacked-by: William Breathitt Gray <william.gray at canonical.com>

> Signed-off-by: William Breathitt Gray <william.gray at canonical.com>
> ---
>  drivers/net/ethernet/mellanox/mlx5/core/eq.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/eq.c b/drivers/net/ethernet/mellanox/mlx5/core/eq.c
> index 0a20938b4aad..938c4a46f9de 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/eq.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/eq.c
> @@ -695,8 +695,10 @@ static void destroy_async_eqs(struct mlx5_core_dev *dev)
>  
>  	cleanup_async_eq(dev, &table->pages_eq, "pages");
>  	cleanup_async_eq(dev, &table->async_eq, "async");
> +	mlx5_cmd_allowed_opcode(dev, MLX5_CMD_OP_DESTROY_EQ);
>  	mlx5_cmd_use_polling(dev);
>  	cleanup_async_eq(dev, &table->cmd_eq, "cmd");
> +	mlx5_cmd_allowed_opcode(dev, CMD_ALLOWED_OPCODE_ALL);
>  	mlx5_eq_notifier_unregister(dev, &table->cq_err_nb);
>  }
>  
> -- 
> 2.27.0
> 
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