IB/mlx4: Report TSO capabilities

Report to the user area the TSO device capabilities, it includes the
max_tso size and the QP types that support it.

The TSO is applicable only when when of the ports is ETH and the device
supports it.

uresp logic around rss_caps is updated to fix a till-now harmless bug
computing the length of the structure to copy. The code did not handle the
implicit padding before rss_caps correctly. This is necessay to copy
tss_caps successfully.

Reviewed-by: Mark Bloch <markb@mellanox.com>
Signed-off-by: Yishai Hadas <yishaih@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/hw/mlx4/main.c

@@ -429,6 +429,9 @@ int mlx4_ib_gid_index_to_real_index(struct mlx4_ib_dev *ibdev,
 	return real_index;
 }
 
+#define field_avail(type, fld, sz) (offsetof(type, fld) + \
+				    sizeof(((type *)0)->fld) <= (sz))
+
 static int mlx4_ib_query_device(struct ib_device *ibdev,
 				struct ib_device_attr *props,
 				struct ib_udata *uhw)
@@ -587,8 +590,7 @@ static int mlx4_ib_query_device(struct ib_device *ibdev,
 			sizeof(struct mlx4_wqe_data_seg);
 	}
 
-	if (uhw->outlen >= resp.response_length + sizeof(resp.rss_caps)) {
-		resp.response_length += sizeof(resp.rss_caps);
+	if (field_avail(typeof(resp), rss_caps, uhw->outlen)) {
 		if (props->rss_caps.supported_qpts) {
 			resp.rss_caps.rx_hash_function =
 				MLX4_IB_RX_HASH_FUNC_TOEPLITZ;
@@ -608,6 +610,22 @@ static int mlx4_ib_query_device(struct ib_device *ibdev,
 				resp.rss_caps.rx_hash_fields_mask |=
 					MLX4_IB_RX_HASH_INNER;
 		}
+		resp.response_length = offsetof(typeof(resp), rss_caps) +
+				       sizeof(resp.rss_caps);
+	}
+
+	if (field_avail(typeof(resp), tso_caps, uhw->outlen)) {
+		if (dev->dev->caps.max_gso_sz &&
+		    ((mlx4_ib_port_link_layer(ibdev, 1) ==
+		    IB_LINK_LAYER_ETHERNET) ||
+		    (mlx4_ib_port_link_layer(ibdev, 2) ==
+		    IB_LINK_LAYER_ETHERNET))) {
+			resp.tso_caps.max_tso = dev->dev->caps.max_gso_sz;
+			resp.tso_caps.supported_qpts |=
+				1 << IB_QPT_RAW_PACKET;
+		}
+		resp.response_length = offsetof(typeof(resp), tso_caps) +
+				       sizeof(resp.tso_caps);
 	}
 
 	if (uhw->outlen) {