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

[William Breathitt Gray]

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)
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