tree 13fc15f92dad0a2307f26ba91e7f4721d0e3ee06
parent a25ce4270bfdd522207b02f81a594c7d1746b697
author Håkon Bugge <haakon.bugge@oracle.com> 1497960470 +0200
committer Doug Ledford <dledford@redhat.com> 1500564050 -0400

IB/mlx4: Fix CM REQ retries in paravirt mode

CM REQs cannot be successfully retried, because a new pv_cm_id is
created for each request, without checking if one already exists.

By checking if an id exists before creating one, the bug is fixed.

This bug can be provoked by running an RDMA CM user-land application,
but inserting a five seconds delay before the rdma_accept() call on
the passive side. This delay is larger than the default CMA timeout,
and triggers a retry from the active side. The retried REQ will use
another pv_cm_id (the cm_id on the wire). This confuses the CM
protocol and two REJs are sent from the passive side.

Here is an excerpt from ibdump running without the patch:

3.285092       LID: 4 -> LID: 4       SDP 290 CM: ConnectRequest(SDP Hello)
7.382711       LID: 4 -> LID: 4       SDP 290 CM: ConnectRequest(SDP Hello)
7.382861       LID: 4 -> LID: 4       InfiniBand 290 CM: ConnectReject
7.387644       LID: 4 -> LID: 4       InfiniBand 290 CM: ConnectReject

and here is the same with bug fix applied:

3.251010       LID: 4 -> LID: 4       SDP 290 CM: ConnectRequest(SDP Hello)
7.349387       LID: 4 -> LID: 4       SDP 290 CM: ConnectRequest(SDP Hello)
8.258443       LID: 4 -> LID: 4       SDP 290 CM: ConnectReply(SDP Hello)
8.259890       LID: 4 -> LID: 4       InfiniBand 290 CM: ReadyToUse

Suggested-by: Venkat Venkatsubra <venkat.x.venkatsubra@oracle.com>
Signed-off-by: Håkon Bugge <haakon.bugge@oracle.com>
Reported-by: Wei Lin Guay <wei.lin.guay@oracle.com>
Tested-by: Wei Lin Guay <wei.lin.guay@oracle.com>
Reviewed-by: Yuval Shaia <yuval.shaia@oracle.com>
Acked-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Doug Ledford <dledford@redhat.com>