diff options
| author | Maxim Mikityanskiy <maximmi@mellanox.com> | 2019-03-27 13:39:21 +0200 |
|---|---|---|
| committer | Saeed Mahameed <saeedm@mellanox.com> | 2019-04-23 12:09:21 -0700 |
| commit | b1b187e1029a374e83942e6c591ee5bf8b60f070 (patch) | |
| tree | 93c95eef33aeeb91957d179fb28f62cf935ed9b4 /drivers/net | |
| parent | 9a22d5d8393fb71a6cc1820c8fb1ef20e26ab149 (diff) | |
net/mlx5e: Add an underflow warning comment
mlx5e_mpwqe_get_log_rq_size calculates the number of WQEs (N) based on
the requested number of frames in the RQ (F) and the number of packets
per WQE (P). It ensures that N is not less than the minimum number of
WQEs in an RQ (N_min). Arithmetically, it means that F / P >= N_min
should be true. This function deals with logarithms, so it should check
that log(F) - log(P) >= log(N_min). However, if F < P, this expression
will cause an unsigned underflow. Check log(F) >= log(P) + log(N_min)
instead.
Signed-off-by: Maxim Mikityanskiy <maximmi@mellanox.com>
Reviewed-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Diffstat (limited to 'drivers/net')
| -rw-r--r-- | drivers/net/ethernet/mellanox/mlx5/core/en/params.c | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/params.c b/drivers/net/ethernet/mellanox/mlx5/core/en/params.c index 658337c3bba1..fa6661ea6310 100644 --- a/drivers/net/ethernet/mellanox/mlx5/core/en/params.c +++ b/drivers/net/ethernet/mellanox/mlx5/core/en/params.c @@ -62,11 +62,14 @@ bool mlx5e_rx_mpwqe_is_linear_skb(struct mlx5_core_dev *mdev, u8 mlx5e_mpwqe_get_log_rq_size(struct mlx5e_params *params) { + u8 log_pkts_per_wqe = mlx5e_mpwqe_log_pkts_per_wqe(params); + + /* Numbers are unsigned, don't subtract to avoid underflow. */ if (params->log_rq_mtu_frames < - mlx5e_mpwqe_log_pkts_per_wqe(params) + MLX5E_PARAMS_MINIMUM_LOG_RQ_SIZE_MPW) + log_pkts_per_wqe + MLX5E_PARAMS_MINIMUM_LOG_RQ_SIZE_MPW) return MLX5E_PARAMS_MINIMUM_LOG_RQ_SIZE_MPW; - return params->log_rq_mtu_frames - mlx5e_mpwqe_log_pkts_per_wqe(params); + return params->log_rq_mtu_frames - log_pkts_per_wqe; } u8 mlx5e_mpwqe_get_log_stride_size(struct mlx5_core_dev *mdev, |