RDMA/rxe: Skip dgid check in loopback mode

In the loopback tests, the following call trace occurs.

 Call Trace:
  __rxe_do_task+0x1a/0x30 [rdma_rxe]
  rxe_qp_destroy+0x61/0xa0 [rdma_rxe]
  rxe_destroy_qp+0x20/0x60 [rdma_rxe]
  ib_destroy_qp_user+0xcc/0x220 [ib_core]
  uverbs_free_qp+0x3c/0xc0 [ib_uverbs]
  destroy_hw_idr_uobject+0x24/0x70 [ib_uverbs]
  uverbs_destroy_uobject+0x43/0x1b0 [ib_uverbs]
  uobj_destroy+0x41/0x70 [ib_uverbs]
  __uobj_get_destroy+0x39/0x70 [ib_uverbs]
  ib_uverbs_destroy_qp+0x88/0xc0 [ib_uverbs]
  ib_uverbs_handler_UVERBS_METHOD_INVOKE_WRITE+0xb9/0xf0 [ib_uverbs]
  ib_uverbs_cmd_verbs+0xb16/0xc30 [ib_uverbs]

The root cause is that the actual RDMA connection is not created in the
loopback tests and the rxe_match_dgid will fail randomly.

To fix this call trace which appear in the loopback tests, skip check of
the dgid.

Fixes: 8700e3e7 ("Soft RoCE driver")
Link: https://lore.kernel.org/r/20200630123605.446959-1-leon@kernel.orgSigned-off-by: Zhu Yanjun <yanjunz@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/sw/rxe/rxe_recv.c

@@ -330,10 +330,14 @@ static void rxe_rcv_mcast_pkt(struct rxe_dev *rxe, struct sk_buff *skb)
 
 static int rxe_match_dgid(struct rxe_dev *rxe, struct sk_buff *skb)
 {
+	struct rxe_pkt_info *pkt = SKB_TO_PKT(skb);
 	const struct ib_gid_attr *gid_attr;
 	union ib_gid dgid;
 	union ib_gid *pdgid;
 
+	if (pkt->mask & RXE_LOOPBACK_MASK)
+		return 0;
+
 	if (skb->protocol == htons(ETH_P_IP)) {
 		ipv6_addr_set_v4mapped(ip_hdr(skb)->daddr,
 				       (struct in6_addr *)&dgid);
@@ -366,7 +370,7 @@ void rxe_rcv(struct sk_buff *skb)
 	if (unlikely(skb->len < pkt->offset + RXE_BTH_BYTES))
 		goto drop;
 
-	if (unlikely(rxe_match_dgid(rxe, skb) < 0)) {
+	if (rxe_match_dgid(rxe, skb) < 0) {
 		pr_warn_ratelimited("failed matching dgid\n");
 		goto drop;
 	}