net/mlx5: Lag, Control MultiPort E-Switch single FDB mode

MultiPort E-Switch builds on newer hardware's capabilities and introduces
a mode where a single E-Switch is used and all the vports and physical
ports on the NIC are connected to it.

The new mode will allow in the future a decrease in the memory used by the
driver and advanced features that aren't possible today.

This represents a big change in the current E-Switch implantation in mlx5.
Currently, by default, each E-Switch manager manages its E-Switch.
Steering rules in each E-Switch can only forward traffic to the native
physical port associated with that E-Switch. While there are ways to target
non-native physical ports, for example using a bond or via special TC
rules. None of the ways allows a user to configure the driver
to operate by default in such a mode nor can the driver decide
to move to this mode by default as it's user configuration-driven right now.

While MultiPort E-Switch single FDB mode is the preferred mode, older
generations of ConnectX hardware couldn't support this mode so it was never
implemented. Now that there is capable hardware present, start the
transition to having this mode by default.

Introduce a devlink parameter to control MultiPort E-Switch single FDB mode.
This will allow users to select this mode on their system right now
and in the future will allow the driver to move to this mode by default.

Example:
    $ devlink dev param set pci/0000:00:0b.0 name esw_multiport value 1 \
                  cmode runtime

Signed-off-by: Roi Dayan <roid@nvidia.com>
Reviewed-by: Maor Dickman <maord@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

Documentation/networking/devlink/mlx5.rst

@@ -54,6 +54,24 @@ parameters.
      - Control the number of large groups (size > 1) in the FDB table.
 
        * The default value is 15, and the range is between 1 and 1024.
+   * - ``esw_multiport``
+     - Boolean
+     - runtime
+     - Control MultiPort E-Switch shared fdb mode.
+
+       An experimental mode where a single E-Switch is used and all the vports
+       and physical ports on the NIC are connected to it.
+
+       An example is to send traffic from a VF that is created on PF0 to an
+       uplink that is natively associated with the uplink of PF1
+
+       Note: Future devices, ConnectX-8 and onward, will eventually have this
+       as the default to allow forwarding between all NIC ports in a single
+       E-switch environment and the dual E-switch mode will likely get
+       deprecated.
+
+       Default: disabled
+
 
 The ``mlx5`` driver supports reloading via ``DEVLINK_CMD_RELOAD``