net/mlx5: qos: Remove qos domains and use shd

E-Switch QoS domains were added with the intention of eventually
implementing shared qos domains to support cross-esw scheduling in the
previous approach ([1]), but they are no longer necessary in the new
approach.

Remove QoS domains and switch to using the shd lock for protecting
against concurrent QoS modifications.
Enable the supported_cross_device_rate_nodes devlink ops attribute so
that all calls originating from devlink rate acquire the shd lock. Only
the additional entry points into QoS need to acquire the shd lock.

The wrinkle is that since shd can be NULL (e.g. on older HW without
serial number available), there needs to be a fallback locking
mechanism. The devlink instance lock cannot be used, as some code paths
into QoS (get, set & modify vport rate) happen with RTNL held, and the
existing devlink -> RTNL order prevents devlink lock usage there.

The other two options are either esw->state_lock or a new lock as
fallback when shd is NULL. This patch adds esw->state_lock, which
implies:

- 3 new lock/unlock helper pairs to acquire/release the missing lock:
  - esw_qos_{,un}lock: acquire/release esw->state_lock when shd is NULL.
  - esw_qos_shd_{,un}lock: when esw->state_lock is already held.
  - esw_qos_devlink_{,un}lock: when shd is already held.
- esw_assert_qos_lock_held now asserts esw->state_lock is held when shd
  is NULL.

Use the corresponding lock/unlock function in all places where either
shd or state_lock would need to be acquired.

Document all of this trickery next to esw_assert_qos_lock_held.

Enabling supported_cross_device_rate_nodes now is safe, because
mlx5_esw_qos_vport_update_parent rejects cross-esw parent updates.
This will change in the next patch.

[1]
https://lore.kernel.org/netdev/20250213180134.323929-1-tariqt@nvidia.com/

Signed-off-by: Cosmin Ratiu <cratiu@nvidia.com>
Reviewed-by: Carolina Jubran <cjubran@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/20260701073254.754518-12-tariqt@nvidia.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

0 files changed, 0 insertions, 0 deletions