Date:   Wed, 1 Aug 2018 15:34:09 -0700
From:   Alexander Duyck <alexander.duyck@...il.com>
To:     Saeed Mahameed <saeedm@...lanox.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Netdev <netdev@...r.kernel.org>, Jiri Pirko <jiri@...lanox.com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Bjorn Helgaas <helgaas@...nel.org>
Subject: Re: [pull request][net-next 00/10] Mellanox, mlx5 and devlink updates 2018-07-31

On Wed, Aug 1, 2018 at 2:52 PM, Saeed Mahameed <saeedm@...lanox.com> wrote:
> Hi Dave,
>
> This series provides devlink parameters updates to both devlink API and
> mlx5 driver, it is a 2nd iteration of the dropped patches sent in a previous
> mlx5 submission "net/mlx5: Support PCIe buffer congestion handling via
> Devlink" to address review comments [1].
>
> Changes from the original series:
> - According to the discussion outcome, we are keeping the congestion control
>   setting as mlx5 device specific for the current HW generation.
> - Changed the congestion_mode and congestion action param type to string
> - Added patches to fix devlink handling of param type string
> - Added a patch which adds extack messages support for param set.
> - At the end of this series, I've added yet another mlx5 devlink related
>  feature, firmware snapshot support.
>
> For more information please see tag log below.
>
> Please pull and let me know if there's any problem.
>
> [1] https://patchwork.ozlabs.org/patch/945996/
>
> Thanks,
> Saeed.
>
> ---
>
> The following changes since commit e6476c21447c4b17c47e476aade6facf050f31e8:
>
>   net: remove bogus RCU annotations on socket.wq (2018-07-31 12:40:22 -0700)
>
> are available in the Git repository at:
>
>   git://git.kernel.org/pub/scm/linux/kernel/git/saeed/linux.git tags/mlx5-updates-2018-08-01
>
> for you to fetch changes up to 2ac6108c65ffcb1e5eab1fba1fd59272604d1c32:
>
>   net/mlx5: Use devlink region_snapshot parameter (2018-08-01 14:49:09 -0700)
>
> ----------------------------------------------------------------
> mlx5-updates-2018-08-01
>
> This series provides devlink parameters updates to both devlink API and
> mlx5 driver,
>
> 1) Devlink changes: (Moshe Shemesh)
> The first two patches fix devlink param infrastructure for string type
> params.
> The third patch adds a devlink helper function to safely copy string from
> driver to devlink.
> The forth patch adds extack support for param set.
>
> 2) mlx5 specific congestion parameters: (Eran Ben Elisha)
> Next three patches add new devlink driver specific params for controlling
> congestion action and mode, using string type params and extack messages support.
>
> This congestion mode enables hw workaround in specific devices which is
> controlled by devlink driver-specific params. The workaround is device
> specific for this NIC generation, the next NIC will not need it.
>
> Congestion parameters:
>  - Congestion action
>             HW W/A mechanism in the PCIe buffer which monitors the amount of
>             consumed PCIe buffer per host.  This mechanism supports the
>             following actions in case of threshold overflow:
>             - Disabled - NOP (Default)
>             - Drop
>             - Mark - Mark CE bit in the CQE of received packet
>     - Congestion mode
>             - Aggressive - Aggressive static trigger threshold (Default)
>             - Dynamic - Dynamically change the trigger threshold
>
> 3) mlx5 firmware snapshot support via devlink: (Alex Vesker)
> Last three patches, add the support for capturing region snapshot of the
> firmware crspace during critical errors, using devlink region_snapshot
> parameter.
>
> -Saeed.
>
> ----------------------------------------------------------------
> Alex Vesker (3):
>       net/mlx5: Add Vendor Specific Capability access gateway
>       net/mlx5: Add Crdump FW snapshot support
>       net/mlx5: Use devlink region_snapshot parameter
>
> Eran Ben Elisha (3):
>       net/mlx5: Move all devlink related functions calls to devlink.c
>       net/mlx5: Add MPEGC register configuration functionality
>       net/mlx5: Enable PCIe buffer congestion handling workaround via devlink
>
> Moshe Shemesh (4):
>       devlink: Fix param set handling for string type
>       devlink: Fix param cmode driverinit for string type
>       devlink: Add helper function for safely copy string param
>       devlink: Add extack messages support to param set
>
>  drivers/net/ethernet/broadcom/bnxt/bnxt_devlink.c  |   3 +-
>  drivers/net/ethernet/mellanox/mlx4/main.c          |   6 +-
>  drivers/net/ethernet/mellanox/mlx5/core/Makefile   |   3 +-
>  drivers/net/ethernet/mellanox/mlx5/core/devlink.c  | 388 +++++++++++++++++++++
>  drivers/net/ethernet/mellanox/mlx5/core/devlink.h  |  13 +
>  .../net/ethernet/mellanox/mlx5/core/diag/crdump.c  | 223 ++++++++++++
>  drivers/net/ethernet/mellanox/mlx5/core/health.c   |   3 +
>  drivers/net/ethernet/mellanox/mlx5/core/lib/mlx5.h |   4 +
>  .../net/ethernet/mellanox/mlx5/core/lib/pci_vsc.c  | 320 +++++++++++++++++
>  .../net/ethernet/mellanox/mlx5/core/lib/pci_vsc.h  |  56 +++
>  drivers/net/ethernet/mellanox/mlx5/core/main.c     |  10 +-
>  include/linux/mlx5/driver.h                        |   5 +
>  include/net/devlink.h                              |  15 +-
>  net/core/devlink.c                                 |  44 ++-
>  14 files changed, 1076 insertions(+), 17 deletions(-)
>  create mode 100644 drivers/net/ethernet/mellanox/mlx5/core/devlink.c
>  create mode 100644 drivers/net/ethernet/mellanox/mlx5/core/devlink.h
>  create mode 100644 drivers/net/ethernet/mellanox/mlx5/core/diag/crdump.c
>  create mode 100644 drivers/net/ethernet/mellanox/mlx5/core/lib/pci_vsc.c
>  create mode 100644 drivers/net/ethernet/mellanox/mlx5/core/lib/pci_vsc.h

So after looking over the patch set the one thing I would ask for in
this is some sort of documentation at a minimum. As a user I don't see
how you can expect someone to be able to use this when the naming of
things are pretty cryptic and there is no real explanation anywhere if
you don't go through and read the patch description itself. When you
start adding driver specific interfaces, you should at least start
adding vendor specific documentation.

Also I don't see how using a vendor specific configuration space
section can be done without adding some tie-ins to the PCI core files
because it should be possible to race with someone poking at the
register space via something like setpci/lspci. Also one of the things
that came up was that drivers are not supposed to be banging on the
PCI configuration space at will, and it seems like this patch set is
doing exactly that through the VSC block.

- Alex

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