RDMA/hns: Add a max length of gid table

IB-core and rdma-core restrict the sgid_index specified by users,
which is uint8_t/u8 data type, to only be within the range of 0-255,
so it's meaningless to support excessively large gid_table_len.

On the other hand, ib-core creates as many sysfs gid files as
gid_table_len, most of which are not only useless because of the
reason above, but also greatly increase the traversal time of
the sysfs gid files for applications.

This patch limits the maximum length of gid table to 256.
Signed-off-by: Junxian Huang <huangjunxian6@hisilicon.com>
Link: https://lore.kernel.org/r/20231207114231.2872104-4-huangjunxian6@hisilicon.comSigned-off-by: Leon Romanovsky <leon@kernel.org>

drivers/infiniband/hw/hns/hns_roce_hw_v2.c

@@ -2060,6 +2060,7 @@ static void set_hem_page_size(struct hns_roce_dev *hr_dev)
 /* Apply all loaded caps before setting to hardware */
 static void apply_func_caps(struct hns_roce_dev *hr_dev)
 {
+#define MAX_GID_TBL_LEN 256
 	struct hns_roce_caps *caps = &hr_dev->caps;
 	struct hns_roce_v2_priv *priv = hr_dev->priv;
 
@@ -2095,8 +2096,14 @@ static void apply_func_caps(struct hns_roce_dev *hr_dev)
 		caps->gmv_entry_sz = HNS_ROCE_V3_GMV_ENTRY_SZ;
 
 		caps->gmv_hop_num = HNS_ROCE_HOP_NUM_0;
-		caps->gid_table_len[0] = caps->gmv_bt_num *
-					(HNS_HW_PAGE_SIZE / caps->gmv_entry_sz);
+
+		/* It's meaningless to support excessively large gid_table_len,
+		 * as the type of sgid_index in kernel struct ib_global_route
+		 * and userspace struct ibv_global_route are u8/uint8_t (0-255).
+		 */
+		caps->gid_table_len[0] = min_t(u32, MAX_GID_TBL_LEN,
+					 caps->gmv_bt_num *
+					 (HNS_HW_PAGE_SIZE / caps->gmv_entry_sz));
 
 		caps->gmv_entry_num = caps->gmv_bt_num * (PAGE_SIZE /
 							  caps->gmv_entry_sz);