-.. BSD LICENSE
- Copyright(c) 2010-2015 Intel Corporation. All rights reserved.
- All rights reserved.
-
- Redistribution and use in source and binary forms, with or without
- modification, are permitted provided that the following conditions
- are met:
-
- * Redistributions of source code must retain the above copyright
- notice, this list of conditions and the following disclaimer.
- * Redistributions in binary form must reproduce the above copyright
- notice, this list of conditions and the following disclaimer in
- the documentation and/or other materials provided with the
- distribution.
- * Neither the name of Intel Corporation nor the names of its
- contributors may be used to endorse or promote products derived
- from this software without specific prior written permission.
-
- THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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- OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+.. SPDX-License-Identifier: BSD-3-Clause
+ Copyright(c) 2010-2015 Intel Corporation.
.. _Poll_Mode_Driver:
Avoiding lock contention is a key issue in a multi-core environment.
To address this issue, PMDs are designed to work with per-core private resources as much as possible.
-For example, a PMD maintains a separate transmit queue per-core, per-port.
+For example, a PMD maintains a separate transmit queue per-core, per-port, if the PMD is not ``DEV_TX_OFFLOAD_MT_LOCKFREE`` capable.
In the same way, every receive queue of a port is assigned to and polled by a single logical core (lcore).
To comply with Non-Uniform Memory Access (NUMA), memory management is designed to assign to each logical core
Multiple logical cores should never share receive or transmit queues for interfaces since this would require global locks and hinder performance.
-Device Identification and Configuration
----------------------------------------
+If the PMD is ``DEV_TX_OFFLOAD_MT_LOCKFREE`` capable, multiple threads can invoke ``rte_eth_tx_burst()``
+concurrently on the same tx queue without SW lock. This PMD feature found in some NICs and useful in the following use cases:
+
+* Remove explicit spinlock in some applications where lcores are not mapped to Tx queues with 1:1 relation.
+
+* In the eventdev use case, avoid dedicating a separate TX core for transmitting and thus
+ enables more scaling as all workers can send the packets.
+
+See `Hardware Offload`_ for ``DEV_TX_OFFLOAD_MT_LOCKFREE`` capability probing details.
+
+Device Identification, Ownership and Configuration
+--------------------------------------------------
Device Identification
~~~~~~~~~~~~~~~~~~~~~
* A port name used to designate the port in console messages, for administration or debugging purposes.
For ease of use, the port name includes the port index.
+Port Ownership
+~~~~~~~~~~~~~~
+The Ethernet devices ports can be owned by a single DPDK entity (application, library, PMD, process, etc).
+The ownership mechanism is controlled by ethdev APIs and allows to set/remove/get a port owner by DPDK entities.
+Allowing this should prevent any multiple management of Ethernet port by different entities.
+
+.. note::
+
+ It is the DPDK entity responsibility to set the port owner before using it and to manage the port usage synchronization between different threads or processes.
+
Device Configuration
~~~~~~~~~~~~~~~~~~~~
Depending on driver capabilities advertised by
``rte_eth_dev_info_get()``, the PMD may support hardware offloading
-feature like checksumming, TCP segmentation or VLAN insertion.
+feature like checksumming, TCP segmentation, VLAN insertion or
+lockfree multithreaded TX burst on the same TX queue.
The support of these offload features implies the addition of dedicated
status bit(s) and value field(s) into the rte_mbuf data structure, along
described in the mbuf API documentation and in the in :ref:`Mbuf Library
<Mbuf_Library>`, section "Meta Information".
+Per-Port and Per-Queue Offloads
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+In the DPDK offload API, offloads are divided into per-port and per-queue offloads as follows:
+
+* A per-queue offloading can be enabled on a queue and disabled on another queue at the same time.
+* A pure per-port offload is the one supported by device but not per-queue type.
+* A pure per-port offloading can't be enabled on a queue and disabled on another queue at the same time.
+* A pure per-port offloading must be enabled or disabled on all queues at the same time.
+* Any offloading is per-queue or pure per-port type, but can't be both types at same devices.
+* Port capabilities = per-queue capabilities + pure per-port capabilities.
+* Any supported offloading can be enabled on all queues.
+
+The different offloads capabilities can be queried using ``rte_eth_dev_info_get()``.
+The ``dev_info->[rt]x_queue_offload_capa`` returned from ``rte_eth_dev_info_get()`` includes all per-queue offloading capabilities.
+The ``dev_info->[rt]x_offload_capa`` returned from ``rte_eth_dev_info_get()`` includes all pure per-port and per-queue offloading capabilities.
+Supported offloads can be either per-port or per-queue.
+
+Offloads are enabled using the existing ``DEV_TX_OFFLOAD_*`` or ``DEV_RX_OFFLOAD_*`` flags.
+Any requested offloading by an application must be within the device capabilities.
+Any offloading is disabled by default if it is not set in the parameter
+``dev_conf->[rt]xmode.offloads`` to ``rte_eth_dev_configure()`` and
+``[rt]x_conf->offloads`` to ``rte_eth_[rt]x_queue_setup()``.
+
+If any offloading is enabled in ``rte_eth_dev_configure()`` by an application,
+it is enabled on all queues no matter whether it is per-queue or
+per-port type and no matter whether it is set or cleared in
+``[rt]x_conf->offloads`` to ``rte_eth_[rt]x_queue_setup()``.
+
+If a per-queue offloading hasn't been enabled in ``rte_eth_dev_configure()``,
+it can be enabled or disabled in ``rte_eth_[rt]x_queue_setup()`` for individual queue.
+A newly added offloads in ``[rt]x_conf->offloads`` to ``rte_eth_[rt]x_queue_setup()`` input by application
+is the one which hasn't been enabled in ``rte_eth_dev_configure()`` and is requested to be enabled
+in ``rte_eth_[rt]x_queue_setup()``. It must be per-queue type, otherwise trigger an error log.
+
Poll Mode Driver API
--------------------
The Ethernet device API exported by the Ethernet PMDs is described in the *DPDK API Reference*.
+.. _ethernet_device_standard_device_arguments:
+
+Ethernet Device Standard Device Arguments
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Standard Ethernet device arguments allow for a set of commonly used arguments/
+parameters which are applicable to all Ethernet devices to be available to for
+specification of specific device and for passing common configuration
+parameters to those ports.
+
+* ``representor`` for a device which supports the creation of representor ports
+ this argument allows user to specify which switch ports to enable port
+ representors for.::
+
+ -w DBDF,representor=0
+ -w DBDF,representor=[0,4,6,9]
+ -w DBDF,representor=[0-31]
+
+Note: PMDs are not required to support the standard device arguments and users
+should consult the relevant PMD documentation to see support devargs.
+
Extended Statistics API
~~~~~~~~~~~~~~~~~~~~~~~
monitoring a single statistic ("rx_errors" in this case), and if that shows
packets being dropped, it can easily retrieve a "set" of statistics using the
IDs array parameter to ``rte_eth_xstats_get_by_id`` function.
+
+NIC Reset API
+~~~~~~~~~~~~~
+
+.. code-block:: c
+
+ int rte_eth_dev_reset(uint16_t port_id);
+
+Sometimes a port has to be reset passively. For example when a PF is
+reset, all its VFs should also be reset by the application to make them
+consistent with the PF. A DPDK application also can call this function
+to trigger a port reset. Normally, a DPDK application would invokes this
+function when an RTE_ETH_EVENT_INTR_RESET event is detected.
+
+It is the duty of the PMD to trigger RTE_ETH_EVENT_INTR_RESET events and
+the application should register a callback function to handle these
+events. When a PMD needs to trigger a reset, it can trigger an
+RTE_ETH_EVENT_INTR_RESET event. On receiving an RTE_ETH_EVENT_INTR_RESET
+event, applications can handle it as follows: Stop working queues, stop
+calling Rx and Tx functions, and then call rte_eth_dev_reset(). For
+thread safety all these operations should be called from the same thread.
+
+For example when PF is reset, the PF sends a message to notify VFs of
+this event and also trigger an interrupt to VFs. Then in the interrupt
+service routine the VFs detects this notification message and calls
+_rte_eth_dev_callback_process(dev, RTE_ETH_EVENT_INTR_RESET, NULL).
+This means that a PF reset triggers an RTE_ETH_EVENT_INTR_RESET
+event within VFs. The function _rte_eth_dev_callback_process() will
+call the registered callback function. The callback function can trigger
+the application to handle all operations the VF reset requires including
+stopping Rx/Tx queues and calling rte_eth_dev_reset().
+
+The rte_eth_dev_reset() itself is a generic function which only does
+some hardware reset operations through calling dev_unint() and
+dev_init(), and itself does not handle synchronization, which is handled
+by application.
+
+The PMD itself should not call rte_eth_dev_reset(). The PMD can trigger
+the application to handle reset event. It is duty of application to
+handle all synchronization before it calls rte_eth_dev_reset().
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