netdev - Re: [PATCH net-next 12/19] devlink: Introduce mdev port flavour

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Date:   Fri, 8 Nov 2019 19:11:19 +0100
From:   Jiri Pirko <jiri@...nulli.us>
To:     Parav Pandit <parav@...lanox.com>
Cc:     Jakub Kicinski <jakub.kicinski@...ronome.com>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Saeed Mahameed <saeedm@...lanox.com>,
        "kwankhede@...dia.com" <kwankhede@...dia.com>,
        "leon@...nel.org" <leon@...nel.org>,
        "cohuck@...hat.com" <cohuck@...hat.com>,
        Jiri Pirko <jiri@...lanox.com>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>
Subject: Re: [PATCH net-next 12/19] devlink: Introduce mdev port flavour

Fri, Nov 08, 2019 at 05:43:43PM CET, parav@...lanox.com wrote:
>
>
>> -----Original Message-----
>> From: Jiri Pirko <jiri@...nulli.us>
>> >> >> On Fri, 8 Nov 2019 01:44:53 +0000, Parav Pandit wrote:
>> >> >> > > I'm talking about netlink attributes. I'm not suggesting to
>> >> >> > > sprintf it all into the phys_port_name.
>> >> >> > >
>> >> >> > I didn't follow your comment. For devlink port show command
>> >> >> > output you said,
>> >> >> >
>> >> >> > "Surely those devices are anchored in on of the PF (or possibly
>> >> >> > VFs) that should be exposed here from the start."
>> >> >> > So I was trying to explain why we don't expose PF/VF detail in
>> >> >> > the port attributes which contains
>> >> >> > (a) flavour
>> >> >> > (b) netdev representor (name derived from phys_port_name)
>> >> >> > (c) mdev alias
>> >> >> >
>> >> >> > Can you please describe which netlink attribute I missed?
>> >> >>
>> >> >> Identification of the PCI device. The PCI devices are not linked
>> >> >> to devlink ports, so the sysfs hierarchy (a) is irrelevant, (b)
>> >> >> may not be visible in multi- host (or SmartNIC).
>> >> >>
>> >> >
>> >> >It's the unique mdev device alias. It is not right to attach to the PCI
>> device.
>> >> >Mdev is bus in itself where devices are identified uniquely. So an
>> >> >alias
>> >> suffice that identity.
>> >>
>> >> Wait a sec. For mdev, what you say is correct. But here we talk about
>> >> devlink_port which is representing this mdev. And this devlink_port
>> >> is very similar to VF devlink_port. It is bound to specific PF (in
>> >> case of mdev it could be PF-VF).
>> >>
>> >But mdev port has unique phys_port_name in system, it incorrect to use
>> PF/VF prefix.
>> 
>> Why incorrect? It is always bound to pf/vf?
>> 
>Because mdev device already identified using its unique alias. Why does it need prefix?
>Mdev core generating the alias is not aware of the prefixes applied devlink. it shouldn't be.
>We want more letters towards uniqueness of the alias and filling it up with such prefixes doesn't make sense.

mdev belongs undev pf/vf, no matter how uniqueue the name/alias is.

Well, I don't really need those in the phys_port_name, mainly simply
because they would not fit. However, I believe that you should fillup
the PF/VF devlink netlink attrs.

Note that we are not talking here about the actual mdev, but rather
devlink_port associated with this mdev. And devlink port should have
this info.


>
>> >What in hypothetical case, mdev is not on top of PCI...
>> 
>> Okay, let's go hypothetical. In that case, it is going to be on top of something
>> else, wouldn't it?
>Yes, it will be. But just because it is on top of something, doesn't mean we include the whole parent dev, its bridge, its rc hierarchy here.
>There should be a need.
>It was needed in PF/VF case due to overlapping numbers of VFs via single devlink instance. You probably missed my reply to Jakub.

Sure. Again, I don't really care about having that in phys_port_name.
But please fillup the attrs.


>Here it is no overlap.
>