[openib-general] CMA: port 2 loopback problems

[Roland Dreier]

    Or> thanks! you have answered to me on a three years old question
    Or> and its RTFM ... the IB "M" is size is sort of "F"
    Or> so... anyway, what DLID should be set in the path of such QPs?
    Or> also per your understanding (and experience...) what is
    Or> happening when the port gets active, does it influence
    Or> loopback QPs or they just keep working as they did before?

The DLID must be the LID of the port.

If the LID changes when the port becomes active then packets sent to
the old LID will start going into the fabric and either disappear or
go to some other port.

There was some discussion on openib-general a year or two ago about
picking a pseudo-random LID for local ports when initializing HCAs, to
allow loopback connections to stay alive in most cases (collisions are
relatively unlikely and the SM should respect existing LIDs...).

 - R.