netdev - Re: [RFC] current devlink extension plan for NICs

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Message-ID: <20200401131231.74f2a5a8@kicinski-fedora-PC1C0HJN>
Date:   Wed, 1 Apr 2020 13:12:31 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Parav Pandit <parav@...lanox.com>
Cc:     Jiri Pirko <jiri@...nulli.us>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        Yuval Avnery <yuvalav@...lanox.com>,
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        Saeed Mahameed <saeedm@...lanox.com>,
        "leon@...nel.org" <leon@...nel.org>,
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        Moshe Shemesh <moshe@...lanox.com>,
        Aya Levin <ayal@...lanox.com>,
        Eran Ben Elisha <eranbe@...lanox.com>,
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Subject: Re: [RFC] current devlink extension plan for NICs

On Wed, 1 Apr 2020 07:32:46 +0000 Parav Pandit wrote:
> > From: Jakub Kicinski <kuba@...nel.org>
> > Sent: Tuesday, March 31, 2020 11:03 PM
> > 
> > On Tue, 31 Mar 2020 07:45:51 +0000 Parav Pandit wrote:  
> > > > In fact very little belongs to the port in that model. So why have
> > > > PCI ports in the first place?
> > > >  
> > > for few reasons.
> > > 1. PCI ports are establishing the relationship between eswitch port
> > > and its representor netdevice.
> > > Relying on plain netdev name doesn't work in certain pci topology
> > > where netdev name exceeds 15 characters.
> > > 2. health reporters can be at port level.  
> > 
> > Why? The health reporters we have not AFAIK are for FW and for queues
> > hanging. Aren't queues on the slice and FW on the device?  
> There are multiple heath reporters per object.
> There are per q health reporters on the representor queues (and
> representors are attached to devlink port). Can someone can have
> representor netdev for an eswitch port without devlink port? No,
> net/core/devlink.c cross verify this and do WARN_ON. So devlink port
> for eswitch are linked to representors and are needed. Their
> existence is not a replacement for representing 'portion of the
> device'.

I don't understand what you're trying to say. My question was why are
queues not on the "slice"? If PCIe resources are on the slice, then so
should be the health reporters.

> > > 3. In future at eswitch pci port, I will be adding dpipe support
> > > for the internal flow tables done by the driver.
> > > 4. There were inconsistency among vendor drivers in using/abusing
> > > phys_port_name of the eswitch ports. This is consolidated via
> > > devlink port in core. This provides consistent view among all
> > > vendor drivers.
> > >
> > > So PCI eswitch side ports are useful regardless of slice.
> > >  
> > > >> Additionally devlink port object doesn't go through the same
> > > >> state machine as that what slice has to go through.
> > > >> So its weird that some devlink port has state machine and some
> > > >> doesn't.  
> > > >
> > > > You mean for VFs? I think you can add the states to the API.
> > > >  
> > > As we agreed above that eswitch side objects (devlink port and
> > > representor netdev) should not be used for 'portion of device',  
> > 
> > We haven't agreed, I just explained how we differ.  
> 
> You mentioned that " Right, in my mental model representor _is_ a
> port of the eswitch, so repr would not make sense to me."
> 
> With that I infer that 'any object that is directly and _always_
> linked to eswitch and represents an eswitch port is out of question,
> this includes devlink port of eswitch and netdev representor. Hence,
> the comment 'we agree conceptually' to not involve devlink port of
> eswitch and representor netdev to represent 'portion of the device'.

I disagree, repr is one to one with eswitch port. Just because
repr is associated with a devlink port doesn't mean devlink port 
must be associated with a repr or a netdev.