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| author | Sagi Grimberg <sagi@grimberg.me> | 2016-03-31 19:03:25 +0300 |
|---|---|---|
| committer | Doug Ledford <dledford@redhat.com> | 2016-04-28 10:49:17 -0400 |
| commit | 986ef95ecdd3eb6fa29433e68faa94c7624083be (patch) | |
| tree | 1b0d6700daf564a1507f8c3226678cf7044d488a /include | |
| parent | 32cc92c7b5e52357a0a24010bae9eb257fa75d3e (diff) | |
| download | linux-986ef95ecdd3eb6fa29433e68faa94c7624083be.tar.gz linux-986ef95ecdd3eb6fa29433e68faa94c7624083be.tar.bz2 linux-986ef95ecdd3eb6fa29433e68faa94c7624083be.zip | |
IB/mlx5: Expose correct max_sge_rd limit
mlx5 devices (Connect-IB, ConnectX-4, ConnectX-4-LX) has a limitation
where rdma read work queue entries cannot exceed 512 bytes.
A rdma_read wqe needs to fit in 512 bytes:
- wqe control segment (16 bytes)
- rdma segment (16 bytes)
- scatter elements (16 bytes each)
So max_sge_rd should be: (512 - 16 - 16) / 16 = 30.
Cc: linux-stable@vger.kernel.org
Reported-by: Christoph Hellwig <hch@lst.de>
Tested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sagi Grimberg <sagig@grimberg.me>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/mlx5/device.h | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/include/linux/mlx5/device.h b/include/linux/mlx5/device.h index 8156e3c9239c..b3575f392492 100644 --- a/include/linux/mlx5/device.h +++ b/include/linux/mlx5/device.h @@ -392,6 +392,17 @@ enum { MLX5_CAP_OFF_CMDIF_CSUM = 46, }; +enum { + /* + * Max wqe size for rdma read is 512 bytes, so this + * limits our max_sge_rd as the wqe needs to fit: + * - ctrl segment (16 bytes) + * - rdma segment (16 bytes) + * - scatter elements (16 bytes each) + */ + MLX5_MAX_SGE_RD = (512 - 16 - 16) / 16 +}; + struct mlx5_inbox_hdr { __be16 opcode; u8 rsvd[4]; |