net/mlx5: Disable QoS when min_rates on all VFs are zero

BugLink: https://bugs.launchpad.net/bugs/1908561

[ Upstream commit 470b747 ]

Currently when QoS is enabled for VF and any min_rate is configured,
the driver sets bw_share value to at least 1 and doesn’t allow to set
it to 0 to make minimal rate unlimited. It means there is always a
minimal rate configured for every VF, even if user tries to remove it.

In order to make QoS disable possible, check whether all vports have
configured min_rate = 0. If this is true, set their bw_share to 0 to
disable min_rate limitations.

Fixes: c9497c9 ("net/mlx5: Add support for setting VF min rate")
Signed-off-by: Vladyslav Tarasiuk <vladyslavt@nvidia.com>
Reviewed-by: Moshe Shemesh <moshe@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Ian May <ian.may@canonical.com>

Author: Hoommus

drivers/net/ethernet/mellanox/mlx5/core/eswitch.c

@@ -2369,12 +2369,15 @@ static u32 calculate_vports_min_rate_divider(struct mlx5_eswitch *esw)
 		max_guarantee = evport->info.min_rate;
 	}
 
-	return max_t(u32, max_guarantee / fw_max_bw_share, 1);
+	if (max_guarantee)
+		return max_t(u32, max_guarantee / fw_max_bw_share, 1);
+	return 0;
 }
 
-static int normalize_vports_min_rate(struct mlx5_eswitch *esw, u32 divider)
+static int normalize_vports_min_rate(struct mlx5_eswitch *esw)
 {
 	u32 fw_max_bw_share = MLX5_CAP_QOS(esw->dev, max_tsar_bw_share);
+	u32 divider = calculate_vports_min_rate_divider(esw);
 	struct mlx5_vport *evport;
 	u32 vport_max_rate;
 	u32 vport_min_rate;
@@ -2387,9 +2390,9 @@ static int normalize_vports_min_rate(struct mlx5_eswitch *esw, u32 divider)
 			continue;
 		vport_min_rate = evport->info.min_rate;
 		vport_max_rate = evport->info.max_rate;
-		bw_share = MLX5_MIN_BW_SHARE;
+		bw_share = 0;
 
-		if (vport_min_rate)
+		if (divider)
 			bw_share = MLX5_RATE_TO_BW_SHARE(vport_min_rate,
 							 divider,
 							 fw_max_bw_share);
@@ -2414,7 +2417,6 @@ int mlx5_eswitch_set_vport_rate(struct mlx5_eswitch *esw, u16 vport,
 	struct mlx5_vport *evport = mlx5_eswitch_get_vport(esw, vport);
 	u32 fw_max_bw_share;
 	u32 previous_min_rate;
-	u32 divider;
 	bool min_rate_supported;
 	bool max_rate_supported;
 	int err = 0;
@@ -2439,8 +2441,7 @@ int mlx5_eswitch_set_vport_rate(struct mlx5_eswitch *esw, u16 vport,
 
 	previous_min_rate = evport->info.min_rate;
 	evport->info.min_rate = min_rate;
-	divider = calculate_vports_min_rate_divider(esw);
-	err = normalize_vports_min_rate(esw, divider);
+	err = normalize_vports_min_rate(esw);
 	if (err) {
 		evport->info.min_rate = previous_min_rate;
 		goto unlock;