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[net,5/6] net/mlx5e: Fix division by 0 in mlx5e_select_queue

Message ID 20210322202524.68886-6-saeed@kernel.org (mailing list archive)
State Accepted
Commit 846d6da1fcdb14105f86b46b4345233550a79d55
Delegated to: Netdev Maintainers
Headers show
Series [net,1/6] net/mlx5: Add back multicast stats for uplink representor | expand

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Context Check Description
netdev/cover_letter success Pull request
netdev/fixes_present success Link
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netdev/tree_selection success Clearly marked for net
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netdev/cc_maintainers warning 2 maintainers not CCed: linux-rdma@vger.kernel.org leon@kernel.org
netdev/source_inline success Was 0 now: 0
netdev/verify_signedoff success Link
netdev/module_param success Was 0 now: 0
netdev/build_32bit success Errors and warnings before: 0 this patch: 0
netdev/kdoc success Errors and warnings before: 0 this patch: 0
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netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 11 lines checked
netdev/build_allmodconfig_warn success Errors and warnings before: 0 this patch: 0
netdev/header_inline success Link

Commit Message

Saeed Mahameed March 22, 2021, 8:25 p.m. UTC 
From: Maxim Mikityanskiy <maximmi@mellanox.com>

mlx5e_select_queue compares num_tc_x_num_ch to real_num_tx_queues to
determine if HTB and/or PTP offloads are active. If they are, it
calculates netdev_pick_tx() % num_tc_x_num_ch to prevent it from
selecting HTB and PTP queues for regular traffic. However, before the
channels are first activated, num_tc_x_num_ch is zero. If
ndo_select_queue gets called at this point, the HTB/PTP check will pass,
and mlx5e_select_queue will attempt to take a modulo by num_tc_x_num_ch,
which equals to zero.

This commit fixes the bug by assigning num_tc_x_num_ch to a non-zero
value before registering the netdev.

Fixes: 214baf22870c ("net/mlx5e: Support HTB offload")
Reported-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Maxim Mikityanskiy <maximmi@mellanox.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
---
 drivers/net/ethernet/mellanox/mlx5/core/en_main.c | 5 +++++
 1 file changed, 5 insertions(+)
diff mbox series

Patch

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
index c8b8249846a9..158f947a8503 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -4979,6 +4979,11 @@  void mlx5e_build_nic_params(struct mlx5e_priv *priv, struct mlx5e_xsk *xsk, u16
 				     priv->max_nch);
 	params->num_tc       = 1;
 
+	/* Set an initial non-zero value, so that mlx5e_select_queue won't
+	 * divide by zero if called before first activating channels.
+	 */
+	priv->num_tc_x_num_ch = params->num_channels * params->num_tc;
+
 	/* SQ */
 	params->log_sq_size = is_kdump_kernel() ?
 		MLX5E_PARAMS_MINIMUM_LOG_SQ_SIZE :