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net/mlx5e: RX, Avoid possible data corruption when relaxed ordering and LRO combined

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When HW aggregates packets for an LRO session, it writes the payload
of two consecutive packets of a flow contiguously, so that they usually
share a cacheline.

The first byte of a packet's payload is written immediately after
the last byte of the preceding packet.
In this flow, there are two consecutive write requests to the shared
cacheline:
1. Regular write for the earlier packet.
2. Read-modify-write for the following packet.

In case of relaxed-ordering on, these two writes might be re-ordered.
Using the end padding optimization (to avoid partial write for the last
cacheline of a packet) becomes problematic if the two writes occur
out-of-order, as the padding would overwrite payload that belongs to
the following packet, causing data corruption.

Avoid this by disabling the end padding optimization when both
LRO and relaxed-ordering are enabled.

Fixes: 17347d5430c4 ("net/mlx5e: Add support for PCI relaxed ordering")
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Moshe Shemesh <moshe@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
This commit is contained in:
Tariq Toukan 2021-06-30 13:45:05 +03:00 committed by Saeed Mahameed
parent dd3fddb827
commit e2351e5170
1 changed files with 10 additions and 1 deletions
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11
drivers/net/ethernet/mellanox/mlx5/core/en/params.c
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@ -471,6 +471,15 @@ static void mlx5e_build_rx_cq_param(struct mlx5_core_dev *mdev,
param->cq_period_mode = params->rx_cq_moderation.cq_period_mode;
}
static u8 rq_end_pad_mode(struct mlx5_core_dev *mdev, struct mlx5e_params *params)
{
bool ro = pcie_relaxed_ordering_enabled(mdev->pdev) &&
MLX5_CAP_GEN(mdev, relaxed_ordering_write);
return ro && params->lro_en ?
MLX5_WQ_END_PAD_MODE_NONE : MLX5_WQ_END_PAD_MODE_ALIGN;
}
int mlx5e_build_rq_param(struct mlx5_core_dev *mdev,
struct mlx5e_params *params,
struct mlx5e_xsk_param *xsk,
@ -508,7 +517,7 @@ int mlx5e_build_rq_param(struct mlx5_core_dev *mdev,
}
MLX5_SET(wq, wq, wq_type, params->rq_wq_type);
MLX5_SET(wq, wq, end_padding_mode, MLX5_WQ_END_PAD_MODE_ALIGN);
MLX5_SET(wq, wq, end_padding_mode, rq_end_pad_mode(mdev, params));
MLX5_SET(wq, wq, log_wq_stride,
mlx5e_get_rqwq_log_stride(params->rq_wq_type, ndsegs));
MLX5_SET(wq, wq, pd, mdev->mlx5e_res.hw_objs.pdn);