Re: [PATCH net-next 03/13] net/mlx5: E-Switch, move devcom init from TC to eswitch layer

[Shay Drori]

On 27/05/2026 15:54, Tariq Toukan wrote:
> From: Shay Drory <shayd@xxxxxxxxxx>
>
> Move the E-swtich devcom component management from TC layer to ESW
> layer.
>
> This refactoring places devcom lifecycle management at the appropriate
> layer and prepares for SD LAG which needs devcom registration
> independent of the TC/representor initialization.
>
> Signed-off-by: Shay Drory <shayd@xxxxxxxxxx>
> Reviewed-by: Mark Bloch <mbloch@xxxxxxxxxx>
> Signed-off-by: Tariq Toukan <tariqt@xxxxxxxxxx>
> ---
>   .../net/ethernet/mellanox/mlx5/core/en_tc.c   | 20 -------------------
>   .../mellanox/mlx5/core/eswitch_offloads.c     |  6 ++++++
>   2 files changed, 6 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c b/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c
> index a9001d1c902f..3846c16c3138 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c
> @@ -5394,8 +5394,6 @@ int mlx5e_tc_esw_init(struct mlx5_rep_uplink_priv *uplink_priv)
>   {
>   	const size_t sz_enc_opts = sizeof(struct tunnel_match_enc_opts);
>   	u8 mapping_id[MLX5_SW_IMAGE_GUID_MAX_BYTES];
> -	struct mlx5_devcom_match_attr attr = {};
> -	struct netdev_phys_item_id ppid;
>   	struct mlx5e_rep_priv *rpriv;
>   	struct mapping_ctx *mapping;
>   	struct mlx5_eswitch *esw;
> @@ -5456,14 +5454,6 @@ int mlx5e_tc_esw_init(struct mlx5_rep_uplink_priv *uplink_priv)
>   		goto err_action_counter;
>   	}
>   
> -	err = netif_get_port_parent_id(priv->netdev, &ppid, false);
> -	if (!err) {
> -		memcpy(&attr.key.buf, &ppid.id, ppid.id_len);
> -		attr.flags = MLX5_DEVCOM_MATCH_FLAGS_NS;
> -		attr.net = mlx5_core_net(esw->dev);
> -		mlx5_esw_offloads_devcom_init(esw, &attr);
> -	}
> -
>   	return 0;
>   
>   err_action_counter:
> @@ -5484,16 +5474,6 @@ int mlx5e_tc_esw_init(struct mlx5_rep_uplink_priv *uplink_priv)
>   
>   void mlx5e_tc_esw_cleanup(struct mlx5_rep_uplink_priv *uplink_priv)
>   {
> -	struct mlx5e_rep_priv *rpriv;
> -	struct mlx5_eswitch *esw;
> -	struct mlx5e_priv *priv;
> -
> -	rpriv = container_of(uplink_priv, struct mlx5e_rep_priv, uplink_priv);
> -	priv = netdev_priv(rpriv->netdev);
> -	esw = priv->mdev->priv.eswitch;
> -
> -	mlx5_esw_offloads_devcom_cleanup(esw);
> -
>   	mlx5e_tc_tun_cleanup(uplink_priv->encap);
>   
>   	mapping_destroy(uplink_priv->tunnel_enc_opts_mapping);
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/eswitch_offloads.c b/drivers/net/ethernet/mellanox/mlx5/core/eswitch_offloads.c
> index 189be11c4c39..d9683d3ea0e7 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/eswitch_offloads.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/eswitch_offloads.c
> @@ -3866,6 +3866,7 @@ bool mlx5_esw_offloads_controller_valid(const struct mlx5_eswitch *esw, u32 cont
>   int esw_offloads_enable(struct mlx5_eswitch *esw)
>   {
>   	u8 mapping_id[MLX5_SW_IMAGE_GUID_MAX_BYTES];
> +	struct mlx5_devcom_match_attr attr = {};
>   	struct mapping_ctx *reg_c0_obj_pool;
>   	struct mlx5_vport *vport;
>   	unsigned long i;
> @@ -3926,6 +3927,10 @@ int esw_offloads_enable(struct mlx5_eswitch *esw)
>   	if (err)
>   		goto err_vports;
>   
> +	memcpy(attr.key.buf, mapping_id, id_len);
> +	attr.flags = MLX5_DEVCOM_MATCH_FLAGS_NS;
> +	attr.net = mlx5_core_net(esw->dev);
> +	mlx5_esw_offloads_devcom_init(esw, &attr);
Sashiko.dev says:
"Does this code introduce a race condition by registering the VF representor
netdevices before the devcom component is initialized?
Because mlx5_eswitch_enable_pf_vf_vports() was called just before this 
block,
it registers the representor netdevices and emits RTM_NEWLINK events.
Userspace tools can then start asynchronously configuring the interfaces.
If userspace attempts to add a TC rule requiring peer flow programming (like
multipath or LAG) before mlx5_esw_offloads_devcom_init() completes, the 
driver
will attempt to access esw->devcom while it is still NULL. Functions like
mlx5_devcom_for_each_peer_begin() will return false, causing the TC rule
addition to fail with -ENODEV."

if devcom is NULL, is_peer_flow_needed() will return false, and
mlx5e_add_fdb_flow() will return success.


Sashiko.dev says:
"Can this unconditional devcom component initialization cause incorrect
pairing of independent devices if the system image GUID is unavailable?
Previously, netif_get_port_parent_id() would fail and safely bypass devcom
registration if the device lacked a valid hardware GUID. Now,
mlx5_query_nic_sw_system_image_guid() is called earlier in this function
and populates mapping_id and id_len.
If the device lacks a valid hardware GUID (id_len == 0), attr.key.buf will
remain filled with zeros (due to the struct initialization). Unconditionally
registering the devcom component via mlx5_esw_offloads_devcom_init()
with this all-zero key could cause multiple independent devices on the
same host to falsely pair with each other."

mlx5_query_nic_sw_system_image_guid() can only fail with -ENOMEM or
on a FW command error. In both cases mlx5 would have failed earlier
and never reached mlx5_esw_offloads_devcom_init().

>   	return 0;
>   
>   err_vports:
> @@ -3970,6 +3975,7 @@ static int esw_offloads_stop(struct mlx5_eswitch *esw,
>   
>   void esw_offloads_disable(struct mlx5_eswitch *esw)
>   {
> +	mlx5_esw_offloads_devcom_cleanup(esw);
>   	mlx5_eswitch_disable_pf_vf_vports(esw);
>   	mlx5_esw_offloads_rep_unload(esw, MLX5_VPORT_UPLINK);
>   	esw_set_passing_vport_metadata(esw, false);