net/mlx5e: Add an underflow warning comment

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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>

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Maxim Mikityanskiy 2019-03-27 13:39:21 +02:00 • committed by Saeed Mahameed

parent 9a22d5d839

commit b1b187e102

1 changed files with 5 additions and 2 deletions

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7

drivers/net/ethernet/mellanox/mlx5/core/en/params.c

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