netdev - RE: [EXT] Re: [PATCH] qed: Enable RDMA relaxed ordering

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Date:   Wed, 25 Aug 2021 09:35:00 +0000
From:   Ariel Elior <aelior@...vell.com>
To:     Jason Gunthorpe <jgg@...pe.ca>
CC:     Leon Romanovsky <leon@...nel.org>, Shai Malin <smalin@...vell.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "malin1024@...il.com" <malin1024@...il.com>,
        RDMA mailing list <linux-rdma@...r.kernel.org>
Subject: RE: [EXT] Re: [PATCH] qed: Enable RDMA relaxed ordering



> -----Original Message-----
> From: Jason Gunthorpe <jgg@...pe.ca>
> Sent: Tuesday, August 24, 2021 10:42 PM
> To: Ariel Elior <aelior@...vell.com>
> Cc: Leon Romanovsky <leon@...nel.org>; Shai Malin
> <smalin@...vell.com>; davem@...emloft.net; kuba@...nel.org;
> netdev@...r.kernel.org; malin1024@...il.com; RDMA mailing list <linux-
> rdma@...r.kernel.org>
> Subject: Re: [EXT] Re: [PATCH] qed: Enable RDMA relaxed ordering
> 
> On Tue, Aug 24, 2021 at 07:16:41PM +0000, Ariel Elior wrote:
> 
> > In our view the qed/qede/qedr/qedi/qedf are separate drivers, hence we
> > used function pointer structures for the communication between them.
> > We use hierarchies of structures of function pointers to group
> > toghether those which have common purposes (dcbx, ll2, Ethernet,
> > rdma). Changing that to flat exported functions for the RDMA protocol is no
> problem if it is preferred by you.
> 
> I wouldn't twist the driver into knots, but you definately should not be using
> function pointers when there is only one implementation, eliminating that
> would be a fine start and looks straightforward.
> 
> Many of the functions in the rdma ops do not look complicated to move, yes,
> it moves around the layering a bit, but that is OK and probably more
> maintainable in the end. eg modify_qp seems fairly disconnected at the first
> couple layers of function calls.
> 
> > In summary - we got the message and will work on it, but this is no
> > small task and may take some time, and will likely not result in total
> > removal of any mention whatsoever of rdma from the core module (but
> > will reduce it considerably).
> 
> I wouldn't go for complete removal, you just need to have a core driver with
> an exported API that makes some sense for the device.
> 
> eg looking at a random op
> 
> qed_iwarp_set_engine_affin()
> 
> Is an "rdma" function but all it does is call
> qed_llh_set_ppfid_affinity()
> 
> So export qed_llh and move the qed_iwarp to the rdma driver
> 
> etc

Got it, and makes sense to me. I get the point on single instance of
function pointers being redundant. We will start work on the
necessary redesign right away. Meanwhile you may see a few
more critical fixes/small features coming from us which are already
queued up internally on our end, which I hope can be accepted
before we perform the changes discussed here.
Thanks,
Ariel




> 
> Jason