netdev - RE: [PATCH net-next v2 4/7] devlink: allow subports on devlink PCI ports

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Date:   Thu, 21 Mar 2019 15:14:53 +0000
From:   Parav Pandit <parav@...lanox.com>
To:     Jiri Pirko <jiri@...nulli.us>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>
CC:     "Samudrala, Sridhar" <sridhar.samudrala@...el.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "oss-drivers@...ronome.com" <oss-drivers@...ronome.com>
Subject: RE: [PATCH net-next v2 4/7] devlink: allow subports on devlink PCI
 ports



> -----Original Message-----
> From: Jiri Pirko <jiri@...nulli.us>
> Sent: Thursday, March 21, 2019 3:45 AM
> To: Jakub Kicinski <jakub.kicinski@...ronome.com>
> Cc: Parav Pandit <parav@...lanox.com>; Samudrala, Sridhar
> <sridhar.samudrala@...el.com>; davem@...emloft.net;
> netdev@...r.kernel.org; oss-drivers@...ronome.com
> Subject: Re: [PATCH net-next v2 4/7] devlink: allow subports on devlink PCI
> ports
> 
> Mon, Mar 18, 2019 at 08:16:42PM CET, jakub.kicinski@...ronome.com
> wrote:
> >On Mon, 18 Mar 2019 13:11:54 +0100, Jiri Pirko wrote:
> >> >> >2. flavour should not be vf/pf, flavour should be hostport, switchport.
> >> >> >Because switch is flat and agnostic of pf/vf/mdev.
> >> >>
> >> >> Not sure. It's good to have this kind of visibility.
> >> >
> >> >Yes, this subthread honestly makes me go from 60% sure to 95% sure
> >> >we shouldn't do the dual object thing :(  Seems like Parav is
> >> >already confused by it and suggests host port can exist without
> >> >switch port :(
> >>
> >> Although I understand your hesitation, the host ports are also
> >> associated with the asic and should be under the devlink instance.
> >> It is just a matter of proper documentation and clear code to avoid
> >> confusions.
> >
> >They are certainly a part and belong to the ASIC, the question in my
> >mind is more along the lines of do we want "one pipe/one port" or is it
> >okay to have multiple software objects of the same kind for those
> >objects.
> >
> >To put it differently - do want a port object for each port of the ASIC
> >or do we want a port object for each netdev..
> 
> Perhaps "port" name of the object is misleading. From the beginning, I ment
> to have it for both switch ports and host ports. I admit that "host port" is a
> bit misleading, as it is not really a port of eswitch, but the counter part. But
> if we introduce another object for that purpose in devlink (like "partititon"),
> it would be a lot of duplication I think.
> 
> Question is, do we need the "host port"? Can't we just put a relation to host
> netdev in the eswitch port.
> 
Can you please explain how does it work for rdma for non sriov use case?
Do we have to create a fake eswitch object?

> So as you suggest, we would have
> devlink_port -+-- switch netdev/ibdev
>               |
> 	      +-- host netdev/ibdev
>

How does this work for rdma to program single node_guid for dual port ibdev?
Did you actually read the recent example I showed in [1]?
[1] https://marc.info/?l=linux-netdev&m=155312521817191&w=2
And why it doesn't address all the use cases of pf/vf/mdev, ibdev, netdev?

> So the "weights" of both switch/host netdev/ibdev to devlink_port relations
> would be equivalent.
> 
> Then, the devlink_port would represent the whole "pipe" with both ends.
> 
> More I think about it, the more it makes sense to me...