RDMA/mlx4: Ensure that maximal send/receive SGE less than supported by HW

In calculating the global maximum number of the Scatter/Gather elements
supported, the following four maximum parameters must be taken into
consideration: max_sg_rq, max_sg_sq, max_desc_sz_rq and max_desc_sz_sq.

However instead of bringing this complexity to query_device, which still
won't be sufficient anyway (the calculations are dependent on QP type),
the safer approach will be to restore old code, which will give us 32
SGEs.

Fixes: 33023fb8 ("IB/core: add max_send_sge and max_recv_sge attributes")
Reported-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/hw/mlx4/main.c

@@ -517,9 +517,11 @@ static int mlx4_ib_query_device(struct ib_device *ibdev,
 	props->page_size_cap	   = dev->dev->caps.page_size_cap;
 	props->max_qp		   = dev->dev->quotas.qp;
 	props->max_qp_wr	   = dev->dev->caps.max_wqes - MLX4_IB_SQ_MAX_SPARE;
-	props->max_send_sge	   = dev->dev->caps.max_sq_sg;
-	props->max_recv_sge	   = dev->dev->caps.max_rq_sg;
-	props->max_sge_rd	   = MLX4_MAX_SGE_RD;
+	props->max_send_sge =
+		min(dev->dev->caps.max_sq_sg, dev->dev->caps.max_rq_sg);
+	props->max_recv_sge =
+		min(dev->dev->caps.max_sq_sg, dev->dev->caps.max_rq_sg);
+	props->max_sge_rd = MLX4_MAX_SGE_RD;
 	props->max_cq		   = dev->dev->quotas.cq;
 	props->max_cqe		   = dev->dev->caps.max_cqes;
 	props->max_mr		   = dev->dev->quotas.mpt;