netdev - RE: [PATCH v2 05/23] ice: Add devlink params support

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Message-ID: <9ae54c8e60fe4036bd3016cfa0798dac@intel.com>
Date:   Thu, 25 Mar 2021 20:10:13 +0000
From:   "Saleem, Shiraz" <shiraz.saleem@...el.com>
To:     Parav Pandit <parav@...dia.com>,
        "dledford@...hat.com" <dledford@...hat.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "davem@...emloft.net" <davem@...emloft.net>
CC:     "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "Ertman, David M" <david.m.ertman@...el.com>,
        "Nguyen, Anthony L" <anthony.l.nguyen@...el.com>
Subject: RE: [PATCH v2 05/23] ice: Add devlink params support

> Subject: RE: [PATCH v2 05/23] ice: Add devlink params support
> 
> Hi Shiraz,
> 
> > From: Shiraz Saleem <shiraz.saleem@...el.com>
> > Sent: Wednesday, March 24, 2021 5:30 AM
> >
> > Add two new runtime RDMA related devlink parameters to ice driver.
> > 'rdma_resource_limits_sel' is driver-specific while 'rdma_protocol' is generic.
> > Configuration changes result in unplugging the auxiliary RDMA device
> > and re- plugging it with updated values for irdma auxiiary driver to
> > consume at
> > drv.probe()
> >
> > Signed-off-by: Shiraz Saleem <shiraz.saleem@...el.com>
> > ---
> >  .../networking/devlink/devlink-params.rst          |   6 +
> >  Documentation/networking/devlink/ice.rst           |  35 +++++
> >  drivers/net/ethernet/intel/ice/ice_devlink.c       | 146
> > ++++++++++++++++++++-
> >  drivers/net/ethernet/intel/ice/ice_devlink.h       |   6 +
> >  drivers/net/ethernet/intel/ice/ice_main.c          |   2 +
> >  include/net/devlink.h                              |   4 +
> >  net/core/devlink.c                                 |   5 +
> >  7 files changed, 202 insertions(+), 2 deletions(-)
> >
> 
> [..]
> > +.. list-table:: Driver-specific parameters implemented
> > +   :widths: 5 5 5 85
> > +
> > +   * - Name
> > +     - Type
> > +     - Mode
> > +     - Description
> > +   * - ``rdma_resource_limits_sel``
> > +     - string
> > +     - runtime
> > +     - Selector to limit the RDMA resources configured for the
> > + device. The
> > range
> > +       is between 0 and 7 with a default value equal to 3. Each
> > + selector
> > supports
> > +       up to the value specified in the table.
> > +          - 0: 128 QPs
> > +          - 1: 1K QPs
> > +          - 2: 2K QPs
> > +          - 3: 4K QPs
> > +          - 4: 16K QPs
> > +          - 5: 64K QPs
> > +          - 6: 128K QPs
> > +          - 7: 256K QPs
> 
> Resources are better represented as devlink resource.
> Such as,
> 
> $ devlink resource set pci/0000:06:00.0 /rdma/max_qps 16384 $ devlink resource
> set pci/0000:06:00.0 /rdma/max_cqs 8192 $ devlink resource set pci/0000:06:00.0
> /rdma/max_mrs 16384
> 

Hi Parav - Thank you for the feedback.

Maybe I am missing something but I see that a devlink hot reload is required to enforce the update?
There isn't really a de-init required of PCI driver entities in this case for this rdma param.
But only an unplug, plug of the auxdev with new value. Intuitively it feels more runtime-ish.

There is also a device powerof2 requirement on the maxqp which I don't see enforceable as it stands.

This is not super-critical for the initial submission but a nice to have. But I do want to brainstorm options.. 

Shiraz