[dpdk-dev] [PATCH 4/4] ethdev: document indirect flow action life cycle

[Dmitry Kozlyuk <dkozlyuk@nvidia.com>]

rte_flow_action_handle_create() did not specify what happens
with an indirect action when device is stopped, possibly reconfigured,
and started again.

It is proposed that indirect actions persisted across such a sequence.
This allows for easier API usage and better HW resources utilization
by saving indirect actions flush and re-creation with associated error
handling and rollback.

If between stop and start a device is reconfigured in a way that is
incompatible with an existing indirect action, PMD is required to report
an error at the device start. This is mandatory, because flow API does
not supply users with capabilities, so this is the only way for a user
to learn that configuration is invalid. Errors are not reported
at configuration stage to give the user a chance to remove or change
offending actions. For example, if number of queues changes and an RSS
indirect action specifies queues that went away, user must update
the action before starting the device. PMD is not allowed to silently
adjust indirect actions (in the same example, to remove queues from
the RSS), so that all configuration is explicit.

Fixes: 4b61b8774be9 ("ethdev: introduce indirect flow action")
Cc: bingz@nvidia.com
Cc: stable@dpdk.org

Signed-off-by: Dmitry Kozlyuk <dkozlyuk@nvidia.com>
Acked-by: Matan Azrad <matan@nvidia.com>
---
 doc/guides/prog_guide/rte_flow.rst | 10 ++++++++++
 lib/ethdev/rte_flow.h              |  4 ++++
 2 files changed, 14 insertions(+)

diff --git a/doc/guides/prog_guide/rte_flow.rst b/doc/guides/prog_guide/rte_flow.rst
index 2b42d5ec8c..06dd06d9a6 100644
--- a/doc/guides/prog_guide/rte_flow.rst
+++ b/doc/guides/prog_guide/rte_flow.rst
@@ -2785,6 +2785,16 @@ updated depend on the type of the ``action`` and different for every type.
 The indirect action specified data (e.g. counter) can be queried by
 ``rte_flow_action_handle_query()``.
 
+Indirect actions persist across device configure, stop, and start.
+If a new configuration is incompatible with an existing indirect action,
+the start operation will fail. "Incompatible" means that if this action
+was destroyed and created again, creation would fail.
+It is a programmer's responsibility to remove or update offending actions.
+
+PMD developers should use the same diagnostics for ``rte_eth_dev_start()``
+as for ``rte_flow_action_handle_create()``. PMD is not allowed to silently
+ignore or correct offending actions.
+
 .. _table_rte_flow_action_handle:
 
 .. table:: INDIRECT
diff --git a/lib/ethdev/rte_flow.h b/lib/ethdev/rte_flow.h
index 70f455d47d..f571a27fe7 100644
--- a/lib/ethdev/rte_flow.h
+++ b/lib/ethdev/rte_flow.h
@@ -3969,6 +3969,10 @@ struct rte_flow_indir_action_conf {
  * The created object handle has single state and configuration
  * across all the flow rules using it.
  *
+ * Indirect actions persist across device configure, stop, and start.
+ * If a new configuration is incompatible with an existing indirect
+ * action, rte_eth_dev_start() will fail.
+ *
  * @param[in] port_id
  *    The port identifier of the Ethernet device.
  * @param[in] conf
-- 
2.25.1