IB/SA: Check dlid before SA agent queries for ClassPortInfo

SA queries SM for class port info when there is a LID_CHANGE event.

When a base lid is configured before fm is started ie when smlid is
not yet assigned, SA handles the LID_CHANGE event and tries query SM
with lid 0. This will cause an hang.

[ 1106.958820] INFO: task kworker/2:0:23 blocked for more than 120 seconds.
[ 1106.965082] Tainted: G O 4.12.0+ #1
[ 1106.969602] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables
 this message.
[ 1106.977227] kworker/2:0 D 0 23 2 0x00000000
[ 1106.977250] Workqueue: infiniband update_ib_cpi [ib_core]
[ 1106.977261] Call Trace:
[ 1106.977273] __schedule+0x28e/0x860
[ 1106.977285] schedule+0x36/0x80
[ 1106.977298] schedule_timeout+0x1a3/0x2e0
[ 1106.977310] ? radix_tree_iter_tag_clear+0x1b/0x20
[ 1106.977322] ? idr_alloc+0x64/0x90
[ 1106.977334] wait_for_completion+0xe3/0x140
[ 1106.977347] ? wake_up_q+0x80/0x80
[ 1106.977369] update_ib_cpi+0x163/0x210 [ib_core]
[ 1106.977381] process_one_work+0x147/0x370
[ 1106.977394] worker_thread+0x4a/0x390
[ 1106.977406] kthread+0x109/0x140
[ 1106.977418] ? process_one_work+0x370/0x370
[ 1106.977430] ? kthread_park+0x60/0x60
[ 1106.977443] ret_from_fork+0x22/0x30

Always ensure a proper smlid is assigned before querying SM for cpi.

Fixes: ee1c60b1bff ("IB/SA: Modify SA to implicitly cache Class Port info")
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Venkata Sandeep Dhanalakota <venkata.s.dhanalakota@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/core/sa_query.c

@@ -1345,6 +1345,7 @@ EXPORT_SYMBOL(ib_init_ah_attr_from_path);
 
 static int alloc_mad(struct ib_sa_query *query, gfp_t gfp_mask)
 {
+	struct rdma_ah_attr ah_attr;
 	unsigned long flags;
 
 	spin_lock_irqsave(&query->port->ah_lock, flags);
@@ -1356,6 +1357,15 @@ static int alloc_mad(struct ib_sa_query *query, gfp_t gfp_mask)
 	query->sm_ah = query->port->sm_ah;
 	spin_unlock_irqrestore(&query->port->ah_lock, flags);
 
+	/*
+	 * Always check if sm_ah has valid dlid assigned,
+	 * before querying for class port info
+	 */
+	if ((rdma_query_ah(query->sm_ah->ah, &ah_attr) < 0) ||
+	    !rdma_is_valid_unicast_lid(&ah_attr)) {
+		kref_put(&query->sm_ah->ref, free_sm_ah);
+		return -EAGAIN;
+	}
 	query->mad_buf = ib_create_send_mad(query->port->agent, 1,
 					    query->sm_ah->pkey_index,
 					    0, IB_MGMT_SA_HDR, IB_MGMT_SA_DATA,

include/rdma/opa_addr.h

@@ -114,4 +114,20 @@ static inline u32 opa_get_mcast_base(u32 nr_top_bits)
 	return (be32_to_cpu(OPA_LID_PERMISSIVE) << (32 - nr_top_bits));
 }
 
+/* Check for a valid unicast LID for non-SM traffic types */
+static inline bool rdma_is_valid_unicast_lid(struct rdma_ah_attr *attr)
+{
+	if (attr->type == RDMA_AH_ATTR_TYPE_IB) {
+		if (!rdma_ah_get_dlid(attr) ||
+		    rdma_ah_get_dlid(attr) >=
+		    be32_to_cpu(IB_MULTICAST_LID_BASE))
+			return false;
+	} else if (attr->type == RDMA_AH_ATTR_TYPE_OPA) {
+		if (!rdma_ah_get_dlid(attr) ||
+		    rdma_ah_get_dlid(attr) >=
+		    opa_get_mcast_base(OPA_MCAST_NR))
+			return false;
+	}
+	return true;
+}
 #endif /* OPA_ADDR_H */