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Date:   Fri, 28 Aug 2020 05:08:43 +0000
From:   Parav Pandit <parav@...dia.com>
To:     Parav Pandit <parav@...dia.com>, 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: netdev-owner@...r.kernel.org <netdev-owner@...r.kernel.org> On
> Behalf Of Parav Pandit
> Sent: Friday, August 28, 2020 9:57 AM
> 
> 
> > From: Jakub Kicinski <kuba@...nel.org>
> > Sent: Friday, August 28, 2020 3:12 AM
> >
> > On Thu, 27 Aug 2020 20:15:01 +0000 Parav Pandit wrote:
> > > > From: Jakub Kicinski <kuba@...nel.org>
> > > >
> > > > 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?
> >
> > If the number of PFs is static it should be possible to understand
> > which one is on which system.
> >
> How? How do we tell that pfnum A means external system.
> Want to avoid such 'implicit' notion.
> 
> > > > 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?
> >
> > You examples only ever have pfnum 0:
> >
> Because both controllers have pfnum 0.
> 
> > From patch 2:
> >
> > $ devlink port show pci/0000:00:08.0/2
> > pci/0000:00:08.0/2: type eth netdev eth7 controller 0 flavour pcivf
> > pfnum 0 vfnum 1 splittable false
> >   function:
> >     hw_addr 00:00:00:00:00:00
> >
> > $ devlink port show -jp pci/0000:00:08.0/2 {
> >     "port": {
> >         "pci/0000:00:08.0/1": {
> >             "type": "eth",
> >             "netdev": "eth7",
> >             "controller": 0,
> >             "flavour": "pcivf",
> >             "pfnum": 0,
> >             "vfnum": 1,
> >             "splittable": false,
> >             "function": {
> >                 "hw_addr": "00:00:00:00:00:00"
> >             }
> >         }
> >     }
> > }
> >
> > From earlier email:
> >
> > 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
> >
> > If you never use pfnum, you can just put the controller ID there, like
> Netronome.
> >
> It likely not going to work for us. Because pfnum is not some randomly
> generated number.
> It is linked to the underlying PCI pf number. {pf0, pf1...} Orchestration sw uses
> this to identify representor of a PF-VF pair.
> 
> Replacing pfnum with controller number breaks this; and it still doesn't tell user
> that it's the pf on other_host.
> 
> So it is used, and would like to continue to use even if there are multiple PFs port
> (that has same pfnum) under the same eswitch.
> 
> In an alternative,
> Currently we have pcipf, pcivf (and pcisf) flavours. May be if we introduce new
> flavour say 'epcipf' to indicate external pci PF/VF/SF ports?
> There can be better name than epcipf. I just put epcipf to differentiate it.
> However these ports have same attributes as pcipf, pcivf, pcisf flavours.
> 
I pressed the send button without an example of an alternative.
Changed eth dev name to be more readable as phys_port_name.

$ devlink port show
pci/0000:00:08.0/1: type eth netdev enp0s8f0_pf0 flavour pcipf pfnum 0
pci/0000:00:08.0/2: type eth netdev enp0s8f0_epf0 flavour epcipf pfnum 0

This naming only go far as long as each multi-host controller is in different eswitch.
When user prefers them under same eswitch, we will again have collision.
Hence, I suggest to use controller number that addressed both the use cases.

I do not know when Mellanox plan to support this mode, but I was told that this is likely.
What about Netronome? Is each host in different eswitch?

$ devlink port show
pci/0000:00:08.0/1: type eth netdev enp0s8f0_pf0 flavour pcipf pfnum 0
pci/0000:00:08.0/2: type eth netdev enp0s8f0_c0pf0 flavour epcipf pfnum 0

This combines the idea of building phys_port_name of pcipf and external_pcipf ports in same way.
At the same time it has the ability to use the controller number.

Secondly, 
I forgot to mention previously that each controller (in multi host) setup consist of 2 PFs on same cable.
So pfnum!=host_number either.

Hence using controller number covering both use cases looks better to me.

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

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