netdev - RE: [PATCH net-next 2/3] devlink: Consider other controller while building phys_port

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Date:   Thu, 27 Aug 2020 20:15:01 +0000
From:   Parav Pandit <parav@...dia.com>
To:     Jakub Kicinski <kuba@...nel.org>
CC:     Parav Pandit <parav@...lanox.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "roid@...lanox.com" <roid@...lanox.com>,
        "saeedm@...lanox.com" <saeedm@...lanox.com>,
        Jiri Pirko <jiri@...dia.com>
Subject: RE: [PATCH net-next 2/3] devlink: Consider other controller while
 building phys_port_name



> From: Jakub Kicinski <kuba@...nel.org>
> Sent: Friday, August 28, 2020 12:02 AM
> 
> On Thu, 27 Aug 2020 04:31:43 +0000 Parav Pandit wrote:
> > > > $ devlink port show looks like below without a controller annotation.
> > > > pci/0000:00:08.0/0: type eth netdev eth5 flavour physical
> > > > pci/0000:00:08.0/1: type eth netdev eth6 flavour pcipf pfnum 0
> > > > pci/0000:00:08.0/2: type eth netdev eth7 flavour pcipf pfnum 0
> > >
> > > How can you have two PF 0? Aaah - by controller you mean hardware
> > > IP, not whoever is controlling the switching! So the chip has
> > > multiple HW controllers, each of which can have multiple PFs?
> > >
> > Hardware IP is one. This IP is plugged into two PCI root complexes.
> > One is eswitch PF, this PF has its own VFs/SFs.
> > Other PF(s) plugged into an second PCI Root complex serving the server
> system.
> > So you are right there are multiple PFs.
> 
> I find it strange that you have pfnum 0 everywhere but then different
> controllers.
There are multiple PFs, connected to different PCI RC. So device has same pfnum for both the PFs.

> For MultiHost at Netronome we've used pfnum to distinguish
> between the hosts. ASIC must have some unique identifiers for each PF.
> 
Yes. there is. It is identified by a unique controller number; internally it is called host_number.
But internal host_number is misleading term as multiple cables of same physical card can be plugged into single host.
So identifying based on a unique (controller) number and matching that up on external cable is desired.

> I'm not aware of any practical reason for creating PFs on one RC without
> reinitializing all the others.
I may be misunderstanding, but how is initialization is related multiple PFs?

> 
> I can see how having multiple controllers may make things clearer, but adding
> another layer of IDs while the one under it is unused (pfnum=0) feels very
> unnecessary.
pfnum=0 is used today. not sure I understand your comment about being unused.
Can you please explain?

Hierarchical naming kind of make sense, but if you have other ideas to annotate the controller, without changing the hardware pfnum, lets discuss.

> 
> > Both the PFs have same PCI BDF.
> 
> BDFs are irrelevant.