IB/cma: Print warning on different inner and header P_Keys

Commit 4c21b5b ("IB/cma: Add net_dev and private data checks to RDMA
CM") added checks for incoming RDMA CM requests that they can be matched to
a netdev based on the P_Key in the BTH of the request. This behavior was
reverted in commit ab3964a ("IB/cma: Use inner P_Key to determine
netdev"), since the mlx5 and ipath drivers didn't send the correct value
in the BTH P_Key.

Since the ipath driver was removed, and the mlx5 driver can now send GSI
packets on different P_Keys, we could revert the patch to let the rdma_cm
module look on the BTH P_Key when deciding to what netdev a packet belongs.
However, that still breaks compatibility with the older drivers.

Change the behavior to print a warning when receiving a request that has a
different BTH P_Key and inner payload P_Key. In the future, after users
have seen the warnings and upgraded their setups, remove the warning and
block these requests.

Signed-off-by: Haggai Eran <haggaie@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/core/cma.c

@@ -1206,13 +1206,21 @@ static int cma_save_req_info(const struct ib_cm_event *ib_event,
 		req->has_gid	= true;
 		req->service_id	= req_param->primary_path->service_id;
 		req->pkey	= be16_to_cpu(req_param->primary_path->pkey);
+		if (req->pkey != req_param->bth_pkey)
+			pr_warn_ratelimited("RDMA CMA: got different BTH P_Key (0x%x) and primary path P_Key (0x%x)\n"
+					    "RDMA CMA: in the future this may cause the request to be dropped\n",
+					    req_param->bth_pkey, req->pkey);
 		break;
 	case IB_CM_SIDR_REQ_RECEIVED:
 		req->device	= sidr_param->listen_id->device;
 		req->port	= sidr_param->port;
 		req->has_gid	= false;
 		req->service_id	= sidr_param->service_id;
 		req->pkey	= sidr_param->pkey;
+		if (req->pkey != sidr_param->bth_pkey)
+			pr_warn_ratelimited("RDMA CMA: got different BTH P_Key (0x%x) and SIDR request payload P_Key (0x%x)\n"
+					    "RDMA CMA: in the future this may cause the request to be dropped\n",
+					    sidr_param->bth_pkey, req->pkey);
 		break;
 	default:
 		return -EINVAL;