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docs: Document the mediated devices within the nodedev driver

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https://bugzilla.redhat.com/show_bug.cgi?id=1452072

Signed-off-by: Erik Skultety <eskultet@redhat.com>
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Erik Skultety 2017-03-29 12:36:31 +02:00
parent 88ef73e13c
commit a0a0b3cf71
2 changed files with 171 additions and 4 deletions
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168
docs/drvnodedev.html.in
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@ -9,7 +9,7 @@
(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.
SR-IOV, NPIV, MDEV, DRM, etc.
</p>
<p>
@ -75,6 +75,7 @@
<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
<code>mdev</code> (<span class="since">Since 3.4.0</span>).
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.
@ -185,5 +186,170 @@
...
&lt;device&gt;</pre>
<h3><a name="MDEVCap">MDEV capability</a></h3>
<p>
A PCI device capable of creating mediated devices will include a nested
capability <code>mdev_types</code> which enumerates all supported mdev
types on the physical device, along with the type attributes available
through sysfs:
</p>
<dl>
<dt><code>type</code></dt>
<dd>
This element describes a mediated device type which acts as an
abstract template defining a resource allocation for instances of this
device type. The element has one attribute <code>id</code> which holds
an official vendor-supplied identifier for the type.
<span class="since">Since 3.4.0</span>
</dd>
<dt><code>name</code></dt>
<dd>
The <code>name</code> element holds a vendor-supplied code name for
the given mediated device type. This is an optional element.
<span class="since">Since 3.4.0</span>
</dd>
<dt><code>deviceAPI</code></dt>
<dd>
The value of this element describes how an instance of the given type
will be presented to the guest by the VFIO framework.
<span class="since">Since 3.4.0</span>
</dd>
<dt><code>availableInstances</code></dt>
<dd>
This element reports the current state of resource allocation. In other
words, how many instances of the given type can still be successfully
created on the physical device.
<span class="since">Since 3.4.0</span>
</dd>
</dl>
<p>
For a more info about mediated devices, refer to the
<a href="#MDEV">paragraph below</a>.
</p>
<pre>
&lt;device&gt;
...
&lt;driver&gt;
&lt;name&gt;nvidia&lt;/name&gt;
&lt;/driver&gt;
&lt;capability type='pci'&gt;
...
&lt;capability type='mdev_types'&gt;
&lt;type id='nvidia-11'&gt;
&lt;name&gt;GRID M60-0B&lt;/name&gt;
&lt;deviceAPI&gt;vfio-pci&lt;/deviceAPI&gt;
&lt;availableInstances&gt;16&lt;/availableInstances&gt;
&lt;/type&gt;
&lt;!-- Here would come the rest of the available mdev types --&gt;
&lt;/capability&gt;
...
&lt;/capability&gt;
&lt;/device&gt;</pre>
<h2><a name="MDEV">Mediated devices (MDEVs)</a></h2>
<p>
Mediated devices (<span class="since">Since 3.2.0</span>) are software
devices defining resource allocation on the backing physical device which
in turn allows the parent physical device's resources to be divided into
several mediated devices, thus sharing the physical device's performance
among multiple guests. Unlike SR-IOV however, where a PCIe device appears
as multiple separate PCIe devices on the host's PCI bus, mediated devices
only appear on the mdev virtual bus. Therefore, no detach/reattach
procedure from/to the host driver procedure is involved even though
mediated devices are used in a direct device assignment manner.
</p>
<p>
The following sub-elements and attributes are exposed within the
<code>capability</code> element:
</p>
<dl>
<dt><code>type</code></dt>
<dd>
This element describes a mediated device type which acts as an
abstract template defining a resource allocation for instances of this
device type. The element has one attribute <code>id</code> which holds
an official vendor-supplied identifier for the type.
<span class="since">Since 3.4.0</span>
</dd>
<dt><code>iommuGroup</code></dt>
<dd>
This element supports a single attribute <code>number</code> which holds
the IOMMU group number the mediated device belongs to.
<span class="since">Since 3.4.0</span>
</dd>
</dl>
<h3>Example of a mediated device</h3>
<pre>
&lt;device&gt;
&lt;name&gt;mdev_4b20d080_1b54_4048_85b3_a6a62d165c01&lt;/name&gt;
&lt;path&gt;/sys/devices/pci0000:00/0000:00:02.0/4b20d080-1b54-4048-85b3-a6a62d165c01&lt;/path&gt;
&lt;parent&gt;pci_0000_06_00_0&lt;/parent&gt;
&lt;driver&gt;
&lt;name&gt;vfio_mdev&lt;/name&gt;
&lt;/driver&gt;
&lt;capability type='mdev'&gt;
&lt;type id='nvidia-11'/&gt;
&lt;iommuGroup number='12'/&gt;
&lt;capability/&gt;
&lt;device/&gt;</pre>
<p>
The support of mediated device's framework in libvirt's node device driver
covers the following features:
</p>
<ul>
<li>
list available mediated devices on the host
(<span class="since">Since 3.4.0</span>)
</li>
<li>
display device details
(<span class="since">Since 3.4.0</span>)
</li>
</ul>
<p>
Because mediated devices are instantiated from vendor specific templates,
simply called 'types', information describing these types is contained
within the parent device's capabilities
(see the example in <a href="#PCI">PCI host devices</a>).
</p>
<p>
To see the supported mediated device types on a specific physical device
use the following:
</p>
<pre>
$ ls /sys/class/mdev_bus/&lt;device&gt;/mdev_supported_types</pre>
<p>
To manually instantiate a mediated device, use one of the following as a
reference:
</p>
<pre>
$ uuidgen &gt; /sys/class/mdev_bus/&lt;device&gt;/mdev_supported_types/&lt;type&gt;/create
...
$ echo &lt;UUID&gt; &gt; /sys/class/mdev_bus/&lt;device&gt;/mdev_supported_types/&lt;type&gt;/create</pre>
<p>
Manual removal of a mediated device is then performed as follows:
</p>
<pre>
$ echo 1 &gt; /sys/bus/mdev/devices/&lt;uuid&gt;/remove</pre>
</body>
</html>

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tools/virsh.pod
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@ -3178,10 +3178,11 @@ for HBA).
List all of the devices available on the node that are known by libvirt.
I<cap> is used to filter the list by capability types, the types must be
separated by comma, e.g. --cap pci,scsi, valid capability types include
separated by comma, e.g. --cap pci,scsi. Valid capability types include
'system', 'pci', 'usb_device', 'usb', 'net', 'scsi_host', 'scsi_target',
'scsi', 'storage', 'fc_host', 'vports', 'scsi_generic', 'drm'.If I<--tree>
is used, the output is formatted in a tree representing parents of each
'scsi', 'storage', 'fc_host', 'vports', 'scsi_generic', 'drm', 'mdev',
'mdev_types'.
If I<--tree> is used, the output is formatted in a tree representing parents of each
node. I<cap> and I<--tree> are mutually exclusive.
=item B<nodedev-reattach> I<nodedev>