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>