netdev - RE: [PATCH net-next 0/3] nfp: support VF multi-queues configuration

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Date:   Tue, 25 Oct 2022 11:39:12 +0000
From:   Yinjun Zhang <yinjun.zhang@...igine.com>
To:     Saeed Mahameed <saeed@...nel.org>
CC:     Jakub Kicinski <kuba@...nel.org>,
        Simon Horman <simon.horman@...igine.com>,
        David Miller <davem@...emloft.net>,
        Paolo Abeni <pabeni@...hat.com>,
        Michael Chan <michael.chan@...adcom.com>,
        Andy Gospodarek <andy@...yhouse.net>,
        Gal Pressman <gal@...dia.com>,
        Jesse Brandeburg <jesse.brandeburg@...el.com>,
        Tony Nguyen <anthony.l.nguyen@...el.com>,
        Edward Cree <ecree.xilinx@...il.com>,
        Vladimir Oltean <vladimir.oltean@....com>,
        Andrew Lunn <andrew@...n.ch>,
        Nole Zhang <peng.zhang@...igine.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        oss-drivers <oss-drivers@...igine.com>
Subject: RE: [PATCH net-next 0/3] nfp: support VF multi-queues configuration

On Date: Tue, 25 Oct 2022 12:05:14 +0100, Saeed Mahameed wrote:
> On 25 Oct 10:41, Yinjun Zhang wrote:
> >On Tue, 25 Oct 2022 08:51:41 +0100, Saeed Mahameed wrote:
> >> The problem with this is that this should be a per function parameter,
> >> devlink params or resources is not the right place for this as this
> >> should be a configuration of a specific devlink object that is not the
> >> parent device (namely devlink port function), otherwise we will have to
> >> deal with ugly string parsing to address the specific vf attributes.
> >>
> >> let's use devlink port:
> >> https://www.kernel.org/doc/html/latest/networking/devlink/devlink-
> >> port.html
> >>
> >> devlink ports have attributes and we should extend attributes to act like
> >> devlink parameters.
> >>
> >>    devlink port function set DEV/PORT_INDEX [ queue_count count ] ...
> >>
> >> https://man7.org/linux/man-pages/man8/devlink-port.8.html
> >
> >Although the vf-max-queue is a per-VF property, it's configured from PF's
> >perspective, so that the overall queue resource can be reallocated among
> VFs.
> >So a devlink object attached to the PF is used to configure, and resource
> seems
> >more appropriate than param.
> >
> 
> devlink port function is an object that's exposed on the PF. It will give
> you a handle on the PF side to every sub-function (vf/sf) exposed via the
> PF.

Sorry, I thought you meant each VF creates a devlink obj. So still one devlink obj
and each VF registers a devlink port, right? But the configuration is supposed to
be done before VFs are created, it maybe not appropriate to register ports before
relevant VFs are created I think.

> 
> can you provide an example of how you imagine the reosurce vf-max-queue
> api
> will look like ?

Two options, 
one is from VF's perspective, you need configure one by one, very straightforward:
```
pci/xxxx:xx:xx.x:
  name max_q size 128 unit entry
    resources:
      name VF0 size 1 unit entry size_min 1 size_max 128 size_gran 1
      name VF1 size 1 unit entry size_min 1 size_max 128 size_gran 1
      ...
```
another is from queue's perspective, several class is supported, not very flexible:
```
pci/xxxx:xx:xx.x:
  name max_q_class size 128 unit entry
    resources:
      # means how many VFs possess max-q-number of 16/8/..1 respectively
      name _16 size 0 unit entry size_min 0 size_max 128 size_gran 1
      name _8 size 0 unit entry size_min 0 size_max 128 size_gran 1
      ...
      name _1 size 0 unit entry size_min 0 size_max 128 size_gran 1
```