Re: [PATCH v5 00/27] IB/Verbs: IB Management Helpers

From: ira.weiny
Date: Mon Apr 27 2015 - 15:22:59 EST

On Fri, Apr 24, 2015 at 02:44:29PM +0000, Liran Liss wrote:
> > From: Michael Wang []
> > [snip]
> > >
> > > Depends on who is "we".
> > > For ULPs, you are probably right.
> > >
> > > However, core services (e.g., mad management, CM, SA) do care about
> > various details.
> > > In some cases, where it doesn't matter, this code will use management
> > helpers.
> > > In other cases, this code will inspect link, transport, and node attributes of
> > rdma devices.
> > >
> > > For example, the CM code has specific code paths for IB, RoCE, and iWARP.
> > > There is no other CM code; there is no reason to abstract 'CM'. This
> > > code will have code paths that depend on various specific details.
> >
> > That's exactly what we want to stop, we have classified the CM to IB and
> > IWARP now :-)
> >
> We don't want to stop code branches that are not abstractions but rather depend
> on the specific technology!
> There is no generic "iWARP CM" - only one.
> There is no generic "ROCE CM" - only one.
> There is no generic "IB CM" - only one.

How can you say this? Or perhaps I don't understand what you mean.

While conceptually one could say that each technology has its own "CM" we are
trying to have the same module (and code) implement them all (ie a generic CM
for a node). Therefore, the CM code _is_ generic. As is the MAD code. This
is the reason we have this problem. We are trying to reuse those modules for
multiple technologies.

> At the CM high-level (i.e., whether an ib_dev port registers an IB client), you could consider
> an rdma_has_cm() call, but this the only place in the code that this check will be called!
> Hence, no need for a generic check.
> You want to stop abstract code that uses IB core infrastructure.

Not sure what you mean here?


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