IB/mlx5: Ensure proper synchronization accessing memory

Call mlx5_ib_populate_pas() before mapping the DMA buffer to ensure
the hardware reads the values written by the CPU.

Found by: Haggai Eran <haggaie@mellanox.com>
Signed-off-by: Eli Cohen <eli@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/hw/mlx5/mr.c

@@ -680,6 +680,10 @@ static struct mlx5_ib_mr *reg_umr(struct ib_pd *pd, struct ib_umem *umem,
 		err = -ENOMEM;
 		goto error;
 	}
+
+	mlx5_ib_populate_pas(dev, umem, page_shift,
+			     mr_align(mr->pas, MLX5_UMR_ALIGN), 1);
+
 	mr->dma = dma_map_single(ddev, mr_align(mr->pas, MLX5_UMR_ALIGN), size,
 				 DMA_TO_DEVICE);
 	if (dma_mapping_error(ddev, mr->dma)) {
@@ -688,9 +692,6 @@ static struct mlx5_ib_mr *reg_umr(struct ib_pd *pd, struct ib_umem *umem,
 		goto error;
 	}
 
-	mlx5_ib_populate_pas(dev, umem, page_shift,
-			     mr_align(mr->pas, MLX5_UMR_ALIGN), 1);
-
 	memset(&wr, 0, sizeof(wr));
 	wr.wr_id = (u64)(unsigned long)mr;
 	prep_umr_reg_wqe(pd, &wr, &sg, mr->dma, npages, mr->mmr.key, page_shift, virt_addr, len, access_flags);