From 8c30b1e683b37d67d7fe827f6ab63174c596494e Mon Sep 17 00:00:00 2001
Message-Id: <8c30b1e683b37d67d7fe827f6ab63174c596494e@dist-git>
From: Erik Skultety <eskultet@redhat.com>
Date: Thu, 18 May 2017 14:02:49 +0200
Subject: [PATCH] docs: Provide a nodedev driver stub documentation
There's lot more to document about the nodedev driver, besides PCI and
SR-IOV (even this might need to be extended), but let's start small-ish
and at least have a page for it linked from the drivers.html.
https://bugzilla.redhat.com/show_bug.cgi?id=1452072
Signed-off-by: Erik Skultety <eskultet@redhat.com>
(cherry picked from commit a94d431dc46070034de7798f572dc1d257542a50)
Signed-off-by: Erik Skultety <eskultet@redhat.com>
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
---
docs/drivers.html.in | 6 +-
docs/drvnodedev.html.in | 189 ++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 194 insertions(+), 1 deletion(-)
create mode 100644 docs/drvnodedev.html.in
diff --git a/docs/drivers.html.in b/docs/drivers.html.in
index be7483b9b..61993861e 100644
--- a/docs/drivers.html.in
+++ b/docs/drivers.html.in
@@ -4,7 +4,11 @@
<body>
<h1>Internal drivers</h1>
- <ul id="toc"></ul>
+ <ul>
+ <li><a href="#hypervisor">Hypervisor drivers</a></li>
+ <li><a href="#storage">Storage drivers</a></li>
+ <li><a href="drvnodedev.html">Node device driver</a></li>
+ </ul>
<p>
The libvirt public API delegates its implementation to one or
diff --git a/docs/drvnodedev.html.in b/docs/drvnodedev.html.in
new file mode 100644
index 000000000..0a3870343
--- /dev/null
+++ b/docs/drvnodedev.html.in
@@ -0,0 +1,189 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
+<html xmlns="http://www.w3.org/1999/xhtml">
+ <body>
+ <h1>Host device management</h1>
+
+ <p>
+ Libvirt provides management of both physical and virtual host devices
+ (historically also referred to as node devices) like USB, PCI, SCSI, and
+ network devices. This also includes various virtualization capabilities
+ which the aforementioned devices provide for utilization, for example
+ SR-IOV, NPIV, DRM, etc.
+ </p>
+
+ <p>
+ The node device driver provides means to list and show details about host
+ devices (<code>virsh nodedev-list</code>,
+ <code>virsh nodedev-dumpxml</code>), which are generic and can be used
+ with all devices. It also provides means to create and destroy devices
+ (<code>virsh nodedev-create</code>, <code>virsh nodedev-destroy</code>)
+ which are meant to be used to create virtual devices, currently only
+ supported by NPIV
+ (<a href="http://wiki.libvirt.org/page/NPIV_in_libvirt">more info about NPIV)</a>).
+ Devices on the host system are arranged in a tree-like hierarchy, with
+ the root node being called <code>computer</code>. The node device driver
+ supports two backends to manage the devices, HAL and udev, with the former
+ being deprecated in favour of the latter.
+ </p>
+
+ <p>
+ The generic format of a host device XML can be seen below.
+ To identify a device both within the host and the device tree hierarchy,
+ the following elements are used:
+ </p>
+ <dl>
+ <dt><code>name</code></dt>
+ <dd>
+ The device's name will be generated by libvirt using the subsystem,
+ like pci and the device's sysfs basename.
+ </dd>
+ <dt><code>path</code></dt>
+ <dd>
+ Fully qualified sysfs path to the device.
+ </dd>
+ <dt><code>parent</code></dt>
+ <dd>
+ This element identifies the parent node in the device hierarchy. The
+ value of the element will correspond with the device parent's
+ <code>name</code> element or <code>computer</code> if the device does
+ not have any parent.
+ </dd>
+ <dt><code>driver</code></dt>
+ <dd>
+ This elements reports the driver in use for this device. The presence
+ of this element in the output XML depends on whether the underlying
+ device manager (most likely udev) exposes information about the
+ driver.
+ </dd>
+ <dt><code>capability</code></dt>
+ <dd>
+ Describes the device in terms of feature support. The element has one
+ mandatory attribute <code>type</code> the value of which determines
+ the type of the device. Currently recognized values for the attribute
+ are:
+ <code>system</code>,
+ <code>pci</code>,
+ <code>usb</code>,
+ <code>usb_device</code>,
+ <code>net</code>,
+ <code>scsi</code>,
+ <code>scsi_host</code> (<span class="since">Since 0.4.7</span>),
+ <code>fc_host</code>,
+ <code>vports</code>,
+ <code>scsi_target</code> (<span class="since">Since 0.7.3</span>),
+ <code>storage</code> (<span class="since">Since 1.0.4</span>),
+ <code>scsi_generic</code> (<span class="since">Since 1.0.7</span>),
+ <code>drm</code> (<span class="since">Since 3.1.0</span>), and
+ This element can be nested in which case it further specifies a
+ device's capability. Refer to specific device types to see more values
+ for the <code>type</code> attribute which are exclusive.
+ </dd>
+ </dl>
+
+ <h2>Basic structure of a node device</h2>
+ <pre>
+<device>
+ <name>pci_0000_00_17_0</name>
+ <path>/sys/devices/pci0000:00/0000:00:17.0</path>
+ <parent>computer</parent>
+ <driver>
+ <name>ahci</name>
+ </driver>
+ <capability type='pci'>
+...
+ </capability>
+</device></pre>
+
+ <ul id="toc"/>
+
+ <h2><a name="PCI">PCI host devices</a></h2>
+ <dl>
+ <dt><code>capability</code></dt>
+ <dd>
+ When used as top level element, the supported values for the
+ <code>type</code> attribute are <code>pci</code> and
+ <code>phys_function</code> (see <a href="#SRIOVCap">SR-IOV below</a>).
+ </dd>
+ </dl>
+ <pre>
+<device>
+ <name>pci_0000_04_00_1</name>
+ <path>/sys/devices/pci0000:00/0000:00:06.0/0000:04:00.1</path>
+ <parent>pci_0000_00_06_0</parent>
+ <driver>
+ <name>igb</name>
+ </driver>
+ <capability type='pci'>
+ <domain>0</domain>
+ <bus>4</bus>
+ <slot>0</slot>
+ <function>1</function>
+ <product id='0x10c9'>82576 Gigabit Network Connection</product>
+ <vendor id='0x8086'>Intel Corporation</vendor>
+ <iommuGroup number='15'>
+ <address domain='0x0000' bus='0x04' slot='0x00' function='0x1'/>
+ </iommuGroup>
+ <numa node='0'/>
+ <pci-express>
+ <link validity='cap' port='1' speed='2.5' width='2'/>
+ <link validity='sta' speed='2.5' width='2'/>
+ </pci-express>
+ </capability>
+</device></pre>
+
+ <p>
+ The XML format for a PCI device stays the same for any further
+ capabilities it supports, a single nested <code><capability></code>
+ element will be included for each capability the device supports.
+ </p>
+
+ <h3><a name="SRIOVCap">SR-IOV capability</a></h3>
+ <p>
+ Single root input/output virtualization (SR-IOV) allows sharing of the
+ PCIe resources by multiple virtual environments. That is achieved by
+ slicing up a single full-featured physical resource called physical
+ function (PF) into multiple devices called virtual functions (VFs) sharing
+ their configuration with the underlying PF. Despite the SR-IOV
+ specification, the amount of VFs that can be created on a PF varies among
+ manufacturers.
+ </p>
+
+ <p>
+ Suppose the NIC <a href="#PCI">above</a> was also SR-IOV capable, it would
+ also include a nested
+ <code><capability></code> element enumerating all virtual
+ functions available on the physical device (physical port) like in the
+ example below.
+ </p>
+
+ <pre>
+<capability type='pci'>
+...
+ <capability type='virt_functions' maxCount='7'>
+ <address domain='0x0000' bus='0x04' slot='0x10' function='0x1'/>
+ <address domain='0x0000' bus='0x04' slot='0x10' function='0x3'/>
+ <address domain='0x0000' bus='0x04' slot='0x10' function='0x5'/>
+ <address domain='0x0000' bus='0x04' slot='0x10' function='0x7'/>
+ <address domain='0x0000' bus='0x04' slot='0x11' function='0x1'/>
+ <address domain='0x0000' bus='0x04' slot='0x11' function='0x3'/>
+ <address domain='0x0000' bus='0x04' slot='0x11' function='0x5'/>
+ </capability>
+...
+</capability></pre>
+ <p>
+ A SR-IOV child device on the other hand, would then report its top level
+ capability type as a <code>phys_function</code> instead:
+ </p>
+
+ <pre>
+<device>
+...
+ <capability type='phys_function'>
+ <address domain='0x0000' bus='0x04' slot='0x00' function='0x0'/>
+ </capability>
+...
+<device></pre>
+
+ </body>
+</html>
--
2.13.0