linux-kernel - [PATCH 5.15 18/32] net/mlx5e: Dont treat small ceil values as unlimited in HTB offload

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Message-Id: <20220204091915.857237511@linuxfoundation.org>
Date:   Fri,  4 Feb 2022 10:22:28 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Maxim Mikityanskiy <maximmi@...dia.com>,
        Tariq Toukan <tariqt@...dia.com>,
        Saeed Mahameed <saeedm@...dia.com>
Subject: [PATCH 5.15 18/32] net/mlx5e: Dont treat small ceil values as unlimited in HTB offload

From: Maxim Mikityanskiy <maximmi@...dia.com>

commit 736dfe4e68b868829a1e89dfef4a44c1580d4478 upstream.

The hardware spec defines max_average_bw == 0 as "unlimited bandwidth".
max_average_bw is calculated as `ceil / BYTES_IN_MBIT`, which can become
0 when ceil is small, leading to an undesired effect of having no
bandwidth limit.

This commit fixes it by rounding up small values of ceil to 1 Mbit/s.

Fixes: 214baf22870c ("net/mlx5e: Support HTB offload")
Signed-off-by: Maxim Mikityanskiy <maximmi@...dia.com>
Reviewed-by: Tariq Toukan <tariqt@...dia.com>
Signed-off-by: Saeed Mahameed <saeedm@...dia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/net/ethernet/mellanox/mlx5/core/en/qos.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/net/ethernet/mellanox/mlx5/core/en/qos.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/qos.c
@@ -553,7 +553,8 @@ static int mlx5e_htb_convert_rate(struct
 
 static void mlx5e_htb_convert_ceil(struct mlx5e_priv *priv, u64 ceil, u32 *max_average_bw)
 {
-	*max_average_bw = div_u64(ceil, BYTES_IN_MBIT);
+	/* Hardware treats 0 as "unlimited", set at least 1. */
+	*max_average_bw = max_t(u32, div_u64(ceil, BYTES_IN_MBIT), 1);
 
 	qos_dbg(priv->mdev, "Convert: ceil %llu -> max_average_bw %u\n",
 		ceil, *max_average_bw);