linux-kernel - [PATCH] vdpa/mlx5: Correct default number of queues when MQ is on

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Message-ID: <20230727172354.68243-2-dtatulea@nvidia.com>
Date:   Thu, 27 Jul 2023 20:23:46 +0300
From:   Dragos Tatulea <dtatulea@...dia.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
CC:     Dragos Tatulea <dtatulea@...dia.com>,
        Eugenio Pérez <eperezma@...hat.com>,
        <virtualization@...ts.linux-foundation.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH] vdpa/mlx5: Correct default number of queues when MQ is on

The standard specifies that the initial number of queues is the
default, which is 1 (1 tx, 1 rx).

Signed-off-by: Dragos Tatulea <dtatulea@...dia.com>
Reviewed-by: Eugenio Pérez <eperezma@...hat.com>
---
 drivers/vdpa/mlx5/net/mlx5_vnet.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
index 9138ef2fb2c8..6b6eb69a8a90 100644
--- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
+++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
@@ -2517,7 +2517,15 @@ static int mlx5_vdpa_set_driver_features(struct vdpa_device *vdev, u64 features)
 	else
 		ndev->rqt_size = 1;
 
-	ndev->cur_num_vqs = 2 * ndev->rqt_size;
+	/* Device must start with 1 queue pair, as per VIRTIO v1.2 spec, section
+	 * 5.1.6.5.5 "Device operation in multiqueue mode":
+	 *
+	 * Multiqueue is disabled by default.
+	 * The driver enables multiqueue by sending a command using class
+	 * VIRTIO_NET_CTRL_MQ. The command selects the mode of multiqueue
+	 * operation, as follows: ...
+	 */
+	ndev->cur_num_vqs = 2;
 
 	update_cvq_info(mvdev);
 	return err;
-- 
2.41.0