Re: [PATCH V1 for-next 3/4] IB/core: Make sure that the PSN does not overflow

[Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>]

On Sun, Feb 01, 2015 at 01:33:30PM +0200, Or Gerlitz wrote:

> >>@@ -860,6 +860,12 @@ int ib_modify_qp_is_ok(enum ib_qp_state cur_state, enum ib_qp_state next_state,
> >>  	if (mask & ~(req_param | opt_param | IB_QP_STATE))
> >>  		return 0;
> >>+	if ((mask & IB_QP_SQ_PSN) && (attr->sq_psn & 0xff000000))
> >>+		return 0;
> >>+
> >>+	if ((mask & IB_QP_RQ_PSN) && (attr->rq_psn & 0xff000000))
> >>+		return 0;
> >>+

> >And since rdmacm has had this longstanding bug of generating > 24
> >bit PSNs, this change seems really scary - very likely to break
> >working systems.
 
> By IBTA the HW can only use 24 bits, also the IB CM also makes sure
> to only encode/decode 24 PSN bits to/from the wire (see the PSN
> related helpers in drivers/infiniband/core/cm_msgs.h), so in that
> respect, I don't see what other bits which are not 24 bits out of
> the 32 generated ones could be of some use to existing applications,
> please clarify.

Maybe you can explain why this check is suddenly important now? It
seems risky with no rational?

Jason
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