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1 change: 1 addition & 0 deletions configs/AM62AX/AM62AX_linux_toc.txt
Original file line number Diff line number Diff line change
Expand Up @@ -73,6 +73,7 @@ linux/Foundational_Components/Kernel/Kernel_Drivers/Network/CPSW-CBS
linux/Foundational_Components/Kernel/Kernel_Drivers/Network/CPSW-IET
linux/Foundational_Components/Kernel/Kernel_Drivers/Network/CPSW-TSN-Tuning
linux/Foundational_Components/Kernel/Kernel_Drivers/Network/NETCONF-YANG
linux/Foundational_Components/Kernel/Kernel_Drivers/Network/XDP
linux/Foundational_Components/Kernel/Kernel_Drivers/PMIC/pmic_tps6594
linux/Foundational_Components/Kernel/Kernel_Drivers/PWM
linux/Foundational_Components/Kernel/Kernel_Drivers/SPI
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1 change: 1 addition & 0 deletions configs/AM62PX/AM62PX_linux_toc.txt
Original file line number Diff line number Diff line change
Expand Up @@ -75,6 +75,7 @@ linux/Foundational_Components/Kernel/Kernel_Drivers/Network/CPSW-CBS
linux/Foundational_Components/Kernel/Kernel_Drivers/Network/CPSW-IET
linux/Foundational_Components/Kernel/Kernel_Drivers/Network/CPSW-TSN-Tuning
linux/Foundational_Components/Kernel/Kernel_Drivers/Network/NETCONF-YANG
linux/Foundational_Components/Kernel/Kernel_Drivers/Network/XDP
#linux/Foundational_Components/Kernel/Kernel_Drivers/PCIe/PCIe_End_Point
#linux/Foundational_Components/Kernel/Kernel_Drivers/PCIe/PCIe_Backplane
#linux/Foundational_Components/Kernel/Kernel_Drivers/PCIe/PCIe_Root_Complex
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1 change: 1 addition & 0 deletions configs/AM62X/AM62X_linux_toc.txt
Original file line number Diff line number Diff line change
Expand Up @@ -72,6 +72,7 @@ linux/Foundational_Components/Kernel/Kernel_Drivers/Network/CPSW-CBS
linux/Foundational_Components/Kernel/Kernel_Drivers/Network/CPSW-IET
linux/Foundational_Components/Kernel/Kernel_Drivers/Network/CPSW-TSN-Tuning
linux/Foundational_Components/Kernel/Kernel_Drivers/Network/NETCONF-YANG
linux/Foundational_Components/Kernel/Kernel_Drivers/Network/XDP
#linux/Foundational_Components/Kernel/Kernel_Drivers/PCIe/PCIe_End_Point
#linux/Foundational_Components/Kernel/Kernel_Drivers/PCIe/PCIe_Backplane
#linux/Foundational_Components/Kernel/Kernel_Drivers/PCIe/PCIe_Root_Complex
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1 change: 1 addition & 0 deletions configs/AM64X/AM64X_linux_toc.txt
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Expand Up @@ -66,6 +66,7 @@ linux/Foundational_Components/Kernel/Kernel_Drivers/Network/NETCONF-YANG
linux/Foundational_Components/Kernel/Kernel_Drivers/Network/HSR_PRP_Non_Offload
linux/Foundational_Components/Kernel/Kernel_Drivers/Network/HSR_Offload
linux/Foundational_Components/Kernel/Kernel_Drivers/Network/PRP_Offload
linux/Foundational_Components/Kernel/Kernel_Drivers/Network/XDP
linux/Foundational_Components/Kernel/Kernel_Drivers/SPI
linux/Foundational_Components/Kernel/Kernel_Drivers/PCIe/PCIe_End_Point
linux/Foundational_Components/Kernel/Kernel_Drivers/PCIe/PCIe_Root_Complex
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1 change: 1 addition & 0 deletions configs/J7200/J7200_linux_toc.txt
Original file line number Diff line number Diff line change
Expand Up @@ -66,6 +66,7 @@ linux/Foundational_Components/Kernel/Kernel_Drivers/Network/CPSW-EST
linux/Foundational_Components/Kernel/Kernel_Drivers/Network/CPSW-CBS
linux/Foundational_Components/Kernel/Kernel_Drivers/Network/CPSW-IET
linux/Foundational_Components/Kernel/Kernel_Drivers/Network/CPSW-TSN-Tuning
linux/Foundational_Components/Kernel/Kernel_Drivers/Network/XDP
linux/Foundational_Components/Kernel/Kernel_Drivers/PCIe/PCIe_End_Point
linux/Foundational_Components/Kernel/Kernel_Drivers/PCIe/PCIe_Root_Complex
linux/Foundational_Components/Kernel/Kernel_Drivers/PMIC/pmic_tps6594
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1 change: 1 addition & 0 deletions configs/J721E/J721E_linux_toc.txt
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Expand Up @@ -70,6 +70,7 @@ linux/Foundational_Components/Kernel/Kernel_Drivers/Network/CPSW-EST
linux/Foundational_Components/Kernel/Kernel_Drivers/Network/CPSW-CBS
linux/Foundational_Components/Kernel/Kernel_Drivers/Network/CPSW-IET
linux/Foundational_Components/Kernel/Kernel_Drivers/Network/CPSW-TSN-Tuning
linux/Foundational_Components/Kernel/Kernel_Drivers/Network/XDP
linux/Foundational_Components/Kernel/Kernel_Drivers/PCIe/PCIe_End_Point
linux/Foundational_Components/Kernel/Kernel_Drivers/PCIe/PCIe_Backplane
linux/Foundational_Components/Kernel/Kernel_Drivers/PCIe/PCIe_Root_Complex
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1 change: 1 addition & 0 deletions configs/J722S/J722S_linux_toc.txt
Original file line number Diff line number Diff line change
Expand Up @@ -67,6 +67,7 @@ linux/Foundational_Components/Kernel/Kernel_Drivers/Network/CPSW-EST
linux/Foundational_Components/Kernel/Kernel_Drivers/Network/CPSW-CBS
linux/Foundational_Components/Kernel/Kernel_Drivers/Network/CPSW-IET
linux/Foundational_Components/Kernel/Kernel_Drivers/Network/CPSW-TSN-Tuning
linux/Foundational_Components/Kernel/Kernel_Drivers/Network/XDP
linux/Foundational_Components/Kernel/Kernel_Drivers/PCIe/PCIe_Root_Complex
linux/Foundational_Components_Power_Management
linux/Foundational_Components/Power_Management/pm_dfs
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Expand Up @@ -90,5 +90,5 @@ For further details regarding the TSN features and testing, refer :ref:`tsn_with

XDP and zero copy
"""""""""""""""""
The CPSW Ethernet Subsystem supports XDP and zero copy features similar to PRU-ICSS Ethernet Subsystem.
For more details refer :ref:`pru_icssg_xdp`.
The CPSW Ethernet Subsystem supports XDP Native Mode, XDP Generic Mode, and Zero-copy mode.
For detailed setup and testing information, refer to :ref:`kernel_xdp`.
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@@ -0,0 +1,238 @@
.. _kernel_xdp:

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===
XDP

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===

.. contents:: :local:
:depth: 3

Introduction
============

XDP (eXpress Data Path) provides a framework for BPF that enables high-performance programmable packet processing in the Linux kernel. It runs the BPF program at the earliest possible point in software, namely at the moment the network driver receives the packet.

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XDP allows running a BPF program just before the skbs are allocated in the driver, the BPF program can look at the packet and return the following things.

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- XDP_DROP :- The packet is dropped right away, without wasting any resources. Useful for firewall etc.
- XDP_ABORTED :- Similar to drop, an exception is generated.
- XDP_PASS :- Pass the packet to kernel stack, i.e. the skbs are allocated and it works normally.
- XDP_TX :- Send the packet back to same NIC with modification(if done by the program).
- XDP_REDIRECT :- Send the packet to another NIC or to the user space through AF_XDP Socket(discussed below).

.. Image:: /images/XDP-packet-processing.png

As explained before, the XDP_REDIRECT sends packets directly to the user space.
This works by using the AF_XDP socket type which was introduced specifically for this usecase.

In this process, the packet is directly sent to the user space without going through the kernel network stack.

.. Image:: /images/xdp-packet.png

Use cases for XDP
-----------------

XDP is particularly useful for these common networking scenarios:

1. **DDoS Mitigation**: High-speed packet filtering and dropping malicious traffic
2. **Load Balancing**: Efficient traffic distribution across multiple servers
3. **Packet Capture**: High-performance network monitoring without performance penalties
4. **Firewalls**: Wire-speed packet filtering based on flexible rule sets
5. **Network Analytics**: Real-time traffic analysis and monitoring
6. **Custom Network Functions**: Specialized packet handling for unique requirements

How to run XDP on EVM
---------------------

The kernel configuration requires the following changes to use XDP:

.. code-block:: console

CONFIG_DEBUG_INFO_BTF=y
CONFIG_BPF_PRELOAD=y
CONFIG_BPF_PRELOAD_UMD=y
CONFIG_BPF_EVENTS=y
CONFIG_BPF_LSM=y
CONFIG_DEBUG_INFO_REDUCED=n
CONFIG_FTRACE=y
CONFIG_XDP_SOCKETS=y

Tools for debugging XDP Applications
-------------------------------------

Debugging tools for XDP development:

- bpftool - For loading and managing BPF programs
- xdpdump - For capturing XDP packet data
- perf - For performance monitoring and analysis
- bpftrace - For tracing BPF program execution

AF_XDP Sockets
==============

AF_XDP is a socket address family specifically designed to work with the XDP framework.
These sockets provide a high-performance interface for user space applications to receive
and transmit network packets directly from the XDP layer, bypassing the traditional kernel networking stack.

Key characteristics of AF_XDP sockets include:

- Direct path from network driver to user space applications
- Shared memory rings for efficient packet transfer
- Minimal overhead compared to traditional socket interfaces
- Optimized for high-throughput, low-latency applications

How AF_XDP Works
----------------

AF_XDP sockets operate through a shared memory mechanism:

1. XDP program intercepts packets at driver level
2. XDP_REDIRECT action sends packets to the socket
3. Shared memory rings (RX/TX/FILL/COMPLETION) manage packet data
4. Userspace application directly accesses the packet data
5. Zero or minimal copying depending on the mode used

The AF_XDP architecture uses several ring buffers:

- **RX Ring**: Received packets ready for consumption
- **TX Ring**: Packets to be transmitted
- **FILL Ring**: Pre-allocated buffers for incoming packets
- **COMPLETION Ring**: Tracks completed TX operations

For more details on AF_XDP please refer to the official documentation: `AF_XDP <https://www.kernel.org/doc/html/latest/networking/af_xdp.html>`_.

XDP Zero-Copy
=============

Introduction to Zero-Copy Mode
-------------------------------

Zero-copy mode is an optimization in AF_XDP that eliminates packet data copying between the kernel and user space. This results in significantly improved performance for high-throughput network applications.

How Zero-Copy Works
-------------------

In standard XDP operation (copy mode), packet data is copied from kernel memory to user space memory when processed. Zero-copy mode eliminates this copy operation by:

1. Using memory-mapped regions shared between the kernel and user space
2. Allowing direct DMA from network hardware into memory accessible by user space applications
3. Managing memory ownership through descriptor rings rather than data movement

This approach provides several benefits:

- Reduced CPU utilization
- Lower memory bandwidth consumption
- Decreased latency for packet processing
- Improved overall throughput

Performance Considerations
--------------------------

When implementing XDP applications, consider these performance factors:

1. **Memory Alignment**: Buffers should be aligned to page boundaries for optimal performance
2. **Batch Processing**: Process multiple packets in batches when possible
3. **Poll Mode**: Use poll() or similar mechanisms to avoid blocking on socket operations
4. **Core Affinity**: Bind application threads to specific CPU cores to reduce cache contention
5. **NUMA Awareness**: Consider NUMA topology when allocating memory for packet buffers

Testing XDP on EVM
==================

The `xdp-tools <https://github.com/xdp-project/xdp-tools>`__ package provides
utility tools for testing XDP and AF_XDP such as `xdp-bench`, `xdp-trafficgen` etc.

TI SDK packages the latest version of ``xdp-tools`` utilities and provides it as part of the SDK.
This allows users to easily test XDP functionality on EVM using these tools.

Both CPSW and ICSSG Ethernet drivers supports Native XDP, Generic XDP, and Zero-copy mode.

.. note::

In case of testing with CPSW please note that when running XDP in Zero-copy mode, non-XDP traffic will be dropped.

**XDP Transmit test** — generate traffic using XDP (copy mode):

.. code-block:: console

xdp-trafficgen udp -m ff:ff:ff:ff:ff:ff <interface>

**XDP Drop test** — receive and drop packets using XDP (copy mode):

.. code-block:: console

xdp-bench xdp-bench drop <interface>

**XDP Pass test** — receive and pass packets through XDP allowing normal network stack processing (copy mode):

.. code-block:: console

xdp-bench xdp-bench pass <interface>

**XDP TX test** — Hairpins (bounces back) received packets on the same interface (copy mode):

.. code-block:: console

xdp-bench xdp-bench tx <interface>

**XDP Redirect test** — Redirects received packets on the from one interface to another (copy mode):

.. code-block:: console

xdp-bench xdp-bench redirect <interface1> <interface2>

**XSK Drop test** — receive and drop packets using AF_XDP socket in zero-copy mode:

.. code-block:: console

xdp-bench xsk-drop -q 0 -C zero-copy <interface>

**XSK Transmit test** — generate traffic using AF_XDP socket in zero-copy mode:

.. code-block:: console

xdp-trafficgen xsk-udp -m ff:ff:ff:ff:ff:ff -q 0 -C zero-copy <interface>`

``xdpsock`` is deprecated and replaced by `xsk-trafficgen` and `xsk-bench` in `xdp-tools` package.
For more details on zero copy testing refer to `xdpsock <https://github.com/xdp-project/bpf-examples/tree/main/AF_XDP-example>`_

Performance Comparison
----------------------

Performance testing shows that zero-copy mode can provide substantial throughput improvements compared to copy mode:

AF_XDP performance while using 64 byte packets for ICSSG (in Kpps):

.. list-table::
:header-rows: 1

* - Benchmark
- XDP-SKB
- XDP-Native
- XDP-Native(ZeroCopy)
* - rxdrop
- 253
- 473
- 656
* - txonly
- 350
- 354
- 855

AF_XDP performance while using 64 byte packets for CPSW (in Kpps):

.. list-table::
:header-rows: 1

* - Benchmark
- XDP-SKB
- XDP-Native
- XDP-Native(ZeroCopy)
* - rxdrop
- 322
- 491
- 845
* - txonly
- 390
- 394
- 723
Original file line number Diff line number Diff line change
Expand Up @@ -44,7 +44,7 @@ Features supported
- Different MII modes for Real-Time Ethernet ports (MII_G_RT1 and MII_G_RT2) on different PRU_ICSSG instances. For example, MII on a PRU_ICSSG1 port, and RGMII on a PRU_ICSSG2 port, is supported.
- IRQ Coalescing also known as interrupt pacing.
- Multi-cast HW filtering
- XDP Native Mode and XDP Generic Mode
- XDP Native Mode, XDP Generic Mode and Zero-copy mode
- Cut Through forwarding
- PHY Interrupt mode for ICSSG2
- Multicast filtering support for VLAN interfaces
Expand All @@ -54,7 +54,6 @@ Features supported
- VLAN HW filtering
- All-multi mode is always enabled
- Different MII modes for Real-Time Ethernet ports (MII_G_RT1 and MII_G_RT2) on a single PRU_ICSSG instance. For example, MII_G_RT1=MII and MII_G_RT2=RGMII.
- XDP with Zero-copy mode

Driver Configuration
####################
Expand Down Expand Up @@ -713,8 +712,8 @@ To turn off PPS,
XDP
###

The PRU_ICSSG Ethernet driver supports Native XDP as well as Generic XDP. XDP with Zero-copy mode is not supported yet.
For detailed setup and how to test XDP please refer to :ref:`pru_icssg_xdp`.
The PRU_ICSSG Ethernet driver supports Native XDP, Generic XDP, and Zero-copy mode.
Refer to :ref:`kernel_xdp` for more details.


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