[ovs-dev] [PATCH 1/8] doc: Add an overview of the 'dpdk' port

[Stephen Finucane]

These ports are used to allow ingress/egress from the host and are
therefore _reasonably_ important. However, there is no clear overview of
what these ports actually are or why things are done the way they are.
Start closing this gap by providing a standalone example of using these
ports along with a little more detailed overview of the binding process.

There is additional cleanup to be done for the DPDK howto, but that will
be done separately.

Signed-off-by: Stephen Finucane <stephen at that.guru>
Cc: Ciara Loftus <ciara.loftus at intel.com>
Cc: Kevin Traynor <ktraynor at redhat.com>
---
 Documentation/topics/dpdk/index.rst |   1 +
 Documentation/topics/dpdk/phy.rst   | 111 ++++++++++++++++++++++++++++++++++++
 2 files changed, 112 insertions(+)
 create mode 100644 Documentation/topics/dpdk/phy.rst

diff --git a/Documentation/topics/dpdk/index.rst b/Documentation/topics/dpdk/index.rst
index da148b323..5f836a6e9 100644
--- a/Documentation/topics/dpdk/index.rst
+++ b/Documentation/topics/dpdk/index.rst
@@ -28,5 +28,6 @@ The DPDK Datapath
 .. toctree::
    :maxdepth: 2
 
+   phy
    vhost-user
    ring
diff --git a/Documentation/topics/dpdk/phy.rst b/Documentation/topics/dpdk/phy.rst
new file mode 100644
index 000000000..1c18e4e3d
--- /dev/null
+++ b/Documentation/topics/dpdk/phy.rst
@@ -0,0 +1,111 @@
+..
+      Copyright 2018, Red Hat, Inc.
+
+      Licensed under the Apache License, Version 2.0 (the "License"); you may
+      not use this file except in compliance with the License. You may obtain
+      a copy of the License at
+
+          http://www.apache.org/licenses/LICENSE-2.0
+
+      Unless required by applicable law or agreed to in writing, software
+      distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+      WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+      License for the specific language governing permissions and limitations
+      under the License.
+
+      Convention for heading levels in Open vSwitch documentation:
+
+      =======  Heading 0 (reserved for the title in a document)
+      -------  Heading 1
+      ~~~~~~~  Heading 2
+      +++++++  Heading 3
+      '''''''  Heading 4
+
+      Avoid deeper levels because they do not render well.
+
+===================
+DPDK Physical Ports
+===================
+
+The DPDK datapath provides a way to attach DPDK-backed physical interfaces to
+allow high-performance ingress/egress from the host.
+
+.. versionchanged:: 2.7.0
+
+   Before Open vSwitch 2.7.0, it was necessary to prefix port names with a
+   ``dpdk`` prefix. Starting with 2.7.0, this is no longer necessary.
+
+Quick Example
+-------------
+
+This example demonstrates how to bind two ``dpdk`` ports, bound to physical
+interfaces identified by hardware IDs ``0000:01:00.0`` and ``0000:01:00.1``, to
+an existing bridge called ``br0``::
+
+    $ ovs-vsctl add-port br0 dpdk-p0 \
+       -- set Interface dpdk-p0 type=dpdk options:dpdk-devargs=0000:01:00.0
+    $ ovs-vsctl add-port br0 dpdk-p1 \
+       -- set Interface dpdk-p1 type=dpdk options:dpdk-devargs=0000:01:00.1
+
+For the above example to work, the two physical interfaces must be bound to
+the DPDK poll-mode drivers in userspace rather than the traditional kernel
+drivers. See the `binding NIC drivers <dpdk-binding-nics>` section for details.
+
+.. _dpdk-binding-nics:
+
+Binding NIC Drivers
+-------------------
+
+DPDK operates entirely in userspace and, as a result, requires use of its own
+poll-mode drivers in user space for physical interfaces and a passthrough-style
+driver for the devices in kernel space.
+
+There are two different tools for binding drivers: :command:`driverctl` which
+is a generic tool for persistently configuring alternative device drivers, and
+:command:`dpdk-devbind` which is a DPDK-specific tool and whose changes do not
+persist across reboots. In addition, there are two options available for this
+kernel space driver - VFIO (Virtual Function I/O) and UIO (Userspace I/O) -
+along with a number of drivers for each option. We will demonstrate examples of
+both tools and will use the ``vfio-pci`` driver, which is the more secure,
+robust driver of those available. More information can be found in the `DPDK
+documentation <dpdk-drivers>`__.
+
+To list devices using :command:`driverctl`, run::
+
+    $ driverctl -v list-devices | grep -i net
+    0000:07:00.0 igb (I350 Gigabit Network Connection (Ethernet Server Adapter I350-T2))
+    0000:07:00.1 igb (I350 Gigabit Network Connection (Ethernet Server Adapter I350-T2))
+
+You can then bind one or more of these devices using the same tool::
+
+    $ driverctl set-override 0000:07:00.0 vfio-pci
+
+Alternatively, to list devices using :command:`dpdk-devbind`, run::
+
+    $ dpdk-devbind --status
+    Network devices using DPDK-compatible driver
+    ============================================
+    <none>
+
+    Network devices using kernel driver
+    ===================================
+    0000:07:00.0 'I350 Gigabit Network Connection 1521' if=enp7s0f0 drv=igb unused=igb_uio
+    0000:07:00.1 'I350 Gigabit Network Connection 1521' if=enp7s0f1 drv=igb unused=igb_uio
+
+    Other Network devices
+    =====================
+    ...
+
+Once again, you can then bind one or more of these devices using the same
+tool::
+
+    $ dpdk-devbind --bind=vfio-pci 0000:07:00.0
+
+.. versionchanged:: 2.6.0
+
+   Open vSwitch 2.6.0 added support for DPDK 16.07, which in turn renamed the
+   former ``dpdk_nic_bind`` tool to ``dpdk-devbind``.
+
+For more information, refer to the `DPDK documentation <dpdk-drivers>`__.
+
+.. _dpdk-drivers: http://dpdk.org/doc/guides/linux_gsg/linux_drivers.html
-- 
2.14.3