IB/mlx5: Fix binary compatibility with libmlx5

Commit c1be5232d2 ("Fix micro UAR allocator") broke binary compatibility
between libmlx5 and mlx5_ib since it defines a different value to the number
of micro UARs per page, leading to wrong calculation in libmlx5. This patch
defines struct mlx5_ib_alloc_ucontext_req_v2 as an extension to struct
mlx5_ib_alloc_ucontext_req.  The extended size is determined in mlx5_ib_alloc_ucontext()
and in case of old library we use uuarn 0 which works fine -- this is
acheived due to create_user_qp() falling back from high to medium then to
low class where low class will return 0.  For new libraries we use the
more sophisticated allocation algorithm.

Signed-off-by: Eli Cohen <eli@mellanox.com>
Reviewed-by: Yann Droneaud <ydroneaud@opteya.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/hw/mlx5/main.c

@@ -536,24 +536,38 @@ static struct ib_ucontext *mlx5_ib_alloc_ucontext(struct ib_device *ibdev,
 						  struct ib_udata *udata)
 {
 	struct mlx5_ib_dev *dev = to_mdev(ibdev);
-	struct mlx5_ib_alloc_ucontext_req req;
+	struct mlx5_ib_alloc_ucontext_req_v2 req;
 	struct mlx5_ib_alloc_ucontext_resp resp;
 	struct mlx5_ib_ucontext *context;
 	struct mlx5_uuar_info *uuari;
 	struct mlx5_uar *uars;
 	int gross_uuars;
 	int num_uars;
+	int ver;
 	int uuarn;
 	int err;
 	int i;
+	int reqlen;
 
 	if (!dev->ib_active)
 		return ERR_PTR(-EAGAIN);
 
-	err = ib_copy_from_udata(&req, udata, sizeof(req));
+	memset(&req, 0, sizeof(req));
+	reqlen = udata->inlen - sizeof(struct ib_uverbs_cmd_hdr);
+	if (reqlen == sizeof(struct mlx5_ib_alloc_ucontext_req))
+		ver = 0;
+	else if (reqlen == sizeof(struct mlx5_ib_alloc_ucontext_req_v2))
+		ver = 2;
+	else
+		return ERR_PTR(-EINVAL);
+
+	err = ib_copy_from_udata(&req, udata, reqlen);
 	if (err)
 		return ERR_PTR(err);
 
+	if (req.flags || req.reserved)
+		return ERR_PTR(-EINVAL);
+
 	if (req.total_num_uuars > MLX5_MAX_UUARS)
 		return ERR_PTR(-ENOMEM);
 
@@ -626,6 +640,7 @@ static struct ib_ucontext *mlx5_ib_alloc_ucontext(struct ib_device *ibdev,
 	if (err)
 		goto out_uars;
 
+	uuari->ver = ver;
 	uuari->num_low_latency_uuars = req.num_low_latency_uuars;
 	uuari->uars = uars;
 	uuari->num_uars = num_uars;

drivers/infiniband/hw/mlx5/qp.c

@@ -430,11 +430,17 @@ static int alloc_uuar(struct mlx5_uuar_info *uuari,
 		break;
 
 	case MLX5_IB_LATENCY_CLASS_MEDIUM:
-		uuarn = alloc_med_class_uuar(uuari);
+		if (uuari->ver < 2)
+			uuarn = -ENOMEM;
+		else
+			uuarn = alloc_med_class_uuar(uuari);
 		break;
 
 	case MLX5_IB_LATENCY_CLASS_HIGH:
-		uuarn = alloc_high_class_uuar(uuari);
+		if (uuari->ver < 2)
+			uuarn = -ENOMEM;
+		else
+			uuarn = alloc_high_class_uuar(uuari);
 		break;
 
 	case MLX5_IB_LATENCY_CLASS_FAST_PATH:

drivers/infiniband/hw/mlx5/user.h

@@ -62,6 +62,13 @@ struct mlx5_ib_alloc_ucontext_req {
 	__u32	num_low_latency_uuars;
 };
 
+struct mlx5_ib_alloc_ucontext_req_v2 {
+	__u32	total_num_uuars;
+	__u32	num_low_latency_uuars;
+	__u32	flags;
+	__u32	reserved;
+};
+
 struct mlx5_ib_alloc_ucontext_resp {
 	__u32	qp_tab_size;
 	__u32	bf_reg_size;

include/linux/mlx5/driver.h

@@ -227,6 +227,7 @@ struct mlx5_uuar_info {
 	 * protect uuar allocation data structs
 	 */
 	struct mutex		lock;
+	u32			ver;
 };
 
 struct mlx5_bf {