netdev - RE: [PATCH net-next v2 5/6] devlink: Introduce controller number

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Message-ID: <DM6PR12MB4330602B6E0B5C4A9C2A0592DC260@DM6PR12MB4330.namprd12.prod.outlook.com>
Date:   Wed, 9 Sep 2020 03:06:18 +0000
From:   Parav Pandit <parav@...dia.com>
To:     Jakub Kicinski <kuba@...nel.org>, Parav Pandit <parav@...lanox.com>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Jiri Pirko <jiri@...dia.com>
Subject: RE: [PATCH net-next v2 5/6] devlink: Introduce controller number



> From: Jakub Kicinski <kuba@...nel.org>
> Sent: Wednesday, September 9, 2020 12:20 AM
> 
> Humm?
> 
> > A devlink instance holds ports of two types of controllers.
> > (1) controller discovered on same system where eswitch resides This is
> > the case where PCI PF/VF of a controller and devlink eswitch instance
> > both are located on a single system.
> > (2) controller located on external host system.
> > This is the case where a controller is located in one system and its
> > devlink eswitch ports are located in a different system.
> >
> > When a devlink eswitch instance serves the devlink ports of both
> > controllers together, PCI PF/VF numbers may overlap.
> > Due to this a unique phys_port_name cannot be constructed.
> >
> > For example in below such system controller-A and controller-B, each
> > has PCI PF pf0 whose eswitch ports are present in controller-A.
> > These results in phys_port_name as "pf0" for both.
> > Similar problem exists for VFs and upcoming Sub functions.
> >
> > An example view of two controller systems:
> >
> >                 -----------------------------------------------------
> >                 |                                                   |
> >                 |           --------- ---------                     |
> > -------------   |           | vf(s) | | sf(s) |                     |
> > | server    |   | -------   ----/---- ---/-----  -------            |
> > | pci rc    |=====| pf0 |______/________/        | pf1 |            |
> > | connection|   | -------                        -------            |
> > -------------   |     | controller-B (no eswitch) (controller num=1)|
> >                 ------|----------------------------------------------
> >                 (internal wire)
> >                       |
> >                 -----------------------------------------------------
> >                 |  devlink eswitch ports and reps                   |
> >                 |  ---------------------------------------------    |
> >                 |  |ctrl-A | ctrl-B | ctrl-A | ctrl-B | ctrl-B |    |
> >                 |  |pf0    | pf0    | pf0vfN | pf0vfN | pf0sfN |    |
> >                 |  ---------------------------------------------    |
> 
>                                        ^^^^^^^^
> 
> ctrl-A doesn't have VFs, but sfs below.
>
Right. Instead of showing too many overlapping devices in both controllers, picked sf ports.
 
> pf1 reprs are not listed.
>
It was hard to cover replicate same topology as that of pf0, so It is omitted.
I guess I should put that note to avoid this confusion.
 
> Perhaps it'd be clearer if controllers where not interleaved?
Yes, Jiri also pointed out to get rid of naming A and B and use numbers.
Little older diagram got it. :-(

> 
> >                 |                                                   |
> >                 |           ---------                               |
> >                 |           | sf(s) |                               |
> >                 | -------   ---/-----    -------                    |
> >                 | | pf0 |_____/          | pf1 |                    |
> >                 | -------                -------                    |
> >                 |                                                   |
> >                 |  local controller-A (eswitch) (controller num=0)  |
> >                 -----------------------------------------------------