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authorSagi Grimberg <sagi@grimberg.me>2016-03-31 19:03:25 +0300
committerDoug Ledford <dledford@redhat.com>2016-04-28 10:49:17 -0400
commit986ef95ecdd3eb6fa29433e68faa94c7624083be (patch)
tree1b0d6700daf564a1507f8c3226678cf7044d488a /include
parent32cc92c7b5e52357a0a24010bae9eb257fa75d3e (diff)
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.h11
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];