netdev - Re: [net-next 16/16] net/mlx5: Support multiport eswitch mode

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Date:   Wed, 18 May 2022 17:21:41 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Saeed Mahameed <saeed@...nel.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        Eli Cohen <elic@...dia.com>, Mark Bloch <mbloch@...dia.com>,
        Saeed Mahameed <saeedm@...dia.com>
Subject: Re: [net-next 16/16] net/mlx5: Support multiport eswitch mode

On Tue, 17 May 2022 23:49:38 -0700 Saeed Mahameed wrote:
> From: Eli Cohen <elic@...dia.com>
> 
> Multiport eswitch mode is a LAG mode that allows to add rules that
> forward traffic to a specific physical port without being affected by LAG
> affinity configuration.
> 
> This mode of operation is mutual exclusive with the other LAG modes used
> by multipath and bonding.
> 
> To make the transition between the modes, we maintain a counter on the
> number of rules specifying one of the uplink representors as the target
> of mirred egress redirect action.
> 
> An example of such rule would be:
> 
> $ tc filter add dev enp8s0f0_0 prot all root flower dst_mac \
>   00:11:22:33:44:55 action mirred egress redirect dev enp8s0f0
> 
> If the reference count just grows to one and LAG is not in use, we
> create the LAG in multiport eswitch mode. Other mode changes are not
> allowed while in this mode. When the reference count reaches zero, we
> destroy the LAG and let other modes be used if needed.
> 
> logic also changed such that if forwarding to some uplink destination
> cannot be guaranteed, we fail the operation so the rule will eventually
> be in software and not in hardware.
> 
> Signed-off-by: Eli Cohen <elic@...dia.com>
> Reviewed-by: Mark Bloch <mbloch@...dia.com>
> Signed-off-by: Saeed Mahameed <saeedm@...dia.com>

GCC 12 also points out that:

drivers/net/ethernet/mellanox/mlx5/core/lag/lag.c: In function ‘mlx5_do_bond’:
drivers/net/ethernet/mellanox/mlx5/core/lag/lag.c:786:28: warning: ‘tracker’ is used uninitialized [-Wuninitialized]
  786 |         struct lag_tracker tracker;
      |                            ^~~~~~~
drivers/net/ethernet/mellanox/mlx5/core/lag/lag.c:786:28: note: ‘tracker’ declared here
  786 |         struct lag_tracker tracker;
      |                            ^~~~~~~