On Mon, 2018-04-23 at 17:58 +0000, Rohit Zambre wrote:
> The calculation of need_uuar_lock rightly accounts for at least 1 medium
> bfreg. However, the user can wrongly request for all but one uuars to be
> low latency uuars.
>
> For example, setting MLX5_TOTAL_UUARS=16 and MLX5_NUM_LOW_LAT_UUARS=15
> doesn't throw any error but the user gets only 14 low latency uuars;
> need_lock for bf_1 evaluates to 1. In this case, the first QP of the
> context is mapped to bf_1 which is not a low latency uuar.
>
> Signed-off-by: Rohit Zambre <rzambre@xxxxxxx>
> ---
> providers/mlx5/mlx5.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/providers/mlx5/mlx5.c b/providers/mlx5/mlx5.c
> index 5590241..2a09a95 100644
> --- a/providers/mlx5/mlx5.c
> +++ b/providers/mlx5/mlx5.c
> @@ -1026,7 +1026,8 @@ static struct verbs_context *mlx5_alloc_context(struct ibv_device *ibdev,
> goto err_free;
> }
>
> - if (low_lat_uuars > tot_uuars - 1) {
> + /* account for at least 1 med bfreg and the 0th uuar */
> + if (low_lat_uuars > tot_uuars - 2) {
> errno = ENOMEM;
> goto err_free;
> }
It would be nice if someone from Mellanox who knows the hardware in more
detail would confirm this and the matching fix for the kernel.
--
Doug Ledford <dledford@xxxxxxxxxx>
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