netdev - [PATCH net 1/4] net/mlx5: DR, select MSIX vector 0 for completion queue creation

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Message-ID: <20241220081505.1286093-2-tariqt@nvidia.com>
Date: Fri, 20 Dec 2024 10:15:02 +0200
From: Tariq Toukan <tariqt@...dia.com>
To: "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>, Eric Dumazet <edumazet@...gle.com>, "Andrew
 Lunn" <andrew+netdev@...n.ch>
CC: <netdev@...r.kernel.org>, Saeed Mahameed <saeedm@...dia.com>, Gal Pressman
	<gal@...dia.com>, Leon Romanovsky <leonro@...dia.com>, Mark Bloch
	<mbloch@...dia.com>, Shahar Shitrit <shshitrit@...dia.com>, Yevgeny Kliteynik
	<kliteyn@...dia.com>, Tariq Toukan <tariqt@...dia.com>
Subject: [PATCH net 1/4] net/mlx5: DR, select MSIX vector 0 for completion queue creation

From: Shahar Shitrit <shshitrit@...dia.com>

When creating a software steering completion queue (CQ), an arbitrary
MSIX vector n is selected. This results in the CQ sharing the same
Ethernet traffic channel n associated with the chosen vector. However,
the value of n is often unpredictable, which can introduce complications
for interrupt monitoring and verification tools.

Moreover, SW steering uses polling rather than event-driven interrupts.
Therefore, there is no need to select any MSIX vector other than the
existing vector 0 for CQ creation.

In light of these factors, and to enhance predictability, we modify the
code to consistently select MSIX vector 0 for CQ creation.

Fixes: 297cccebdc5a ("net/mlx5: DR, Expose an internal API to issue RDMA operations")
Signed-off-by: Shahar Shitrit <shshitrit@...dia.com>
Reviewed-by: Yevgeny Kliteynik <kliteyn@...dia.com>
Signed-off-by: Tariq Toukan <tariqt@...dia.com>
---
 .../net/ethernet/mellanox/mlx5/core/steering/sws/dr_send.c    | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/steering/sws/dr_send.c b/drivers/net/ethernet/mellanox/mlx5/core/steering/sws/dr_send.c
index 6fa06ba2d346..f57c84e5128b 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/steering/sws/dr_send.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/steering/sws/dr_send.c
@@ -1067,7 +1067,6 @@ static struct mlx5dr_cq *dr_create_cq(struct mlx5_core_dev *mdev,
 	int inlen, err, eqn;
 	void *cqc, *in;
 	__be64 *pas;
-	int vector;
 	u32 i;
 
 	cq = kzalloc(sizeof(*cq), GFP_KERNEL);
@@ -1096,8 +1095,7 @@ static struct mlx5dr_cq *dr_create_cq(struct mlx5_core_dev *mdev,
 	if (!in)
 		goto err_cqwq;
 
-	vector = raw_smp_processor_id() % mlx5_comp_vectors_max(mdev);
-	err = mlx5_comp_eqn_get(mdev, vector, &eqn);
+	err = mlx5_comp_eqn_get(mdev, 0, &eqn);
 	if (err) {
 		kvfree(in);
 		goto err_cqwq;
-- 
2.45.0