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docs: mention domain <clock> improvements

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Add documentation for features added a while ago.

* docs/formatdomain.html.in (Time keeping): Update documentation
of <clock> element to match 0.8.0 addition.
This commit is contained in:
Eric Blake 2010-05-13 16:00:14 -06:00
parent b8564da17a
commit 2ad42978ea
1 changed files with 71 additions and 5 deletions
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docs/formatdomain.html.in
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@ -411,13 +411,18 @@
<pre>
...
&lt;clock offset="localtime"/&gt;
&lt;clock offset="localtime"&gt;
&lt;timer name="rtc" tickpolicy="catchup" track="guest"&gt;
&lt;catchup threshold=123 slew=120 limit=10000/&gt;
&lt;/timer&gt;
&lt;timer name="pit" tickpolicy="none"/&gt;
&lt;/clock&gt;
...</pre>
<dl>
<dt><code>clock</code></dt>
<dd>
<p>The <code>offset</code> attribute takes three possible
<p>The <code>offset</code> attribute takes four possible
values, allowing fine grained control over how the guest
clock is synchronized to the host. NB, not all hypervisors
support all modes.</p>
@ -435,6 +440,7 @@
<dd>
The guest clock will be synchronized to the requested timezone
using the <code>timezone</code> attribute.
<span class="since">Since 0.7.7</span>
</dd>
<dt><code>variable</code></dt>
<dd>
@ -444,14 +450,74 @@
The guest is free to adjust the RTC over time an expect
that it will be honoured at next reboot. This is in
contrast to 'utc' mode, where the RTC adjustments are
lost at each reboot.
lost at each reboot. <span class="since">Since 0.7.7</span>
</dd>
</dl>
<p>
NB, at time of writing, only QEMU supports the variable
clock mode, or custom timezones.
A <code>clock</code> may have zero or more
<code>timer</code>sub-elements. <span class="since">Since
0.8.0</span>
</p>
</dd>
<dt><code>timer</code></dt>
<dd>
<p>
Each timer element requires a <code>name</code> attribute,
and has other optional attributes that depend on
the <code>name</code> specified. Various hypervisors
support different combinations of attributes.
</p>
<dl>
<dt><code>name</code></dt>
<dd>
The <code>name</code> attribute selects which timer is
being modified, and can be one of "platform", "pit",
"rtc", "hpet", or "tsc".
</dd>
<dt><code>track</code></dt>
<dd>
The <code>track</code> attribute specifies what the timer
tracks, and can be "boot", "guest", or "wall".
Only valid for <code>name="rtc"</code>
or <code>name="platform"</code>.
</dd>
<dt><code>tickpolicy</code></dt>
<dd>
The <code>tickpolicy</code> attribute determines how
missed ticks in the guest are handled, and can be "delay",
"catchup", "merge", or "discard". If the policy is
"catchup", there can be further details in
the <code>catchup</code> sub-element.
<dl>
<dt><code>catchup</code></dt>
<dd>
The <code>catchup</code> element has three optional
attributes, each a positive integer. The attributes
are <code>threshold</code>, <code>slew</code>,
and <code>limit</code>.
</dd>
</dl>
</dd>
<dt><code>frequency</code></dt>
<dd>
The <code>frequency</code> attribute is an unsigned
integer specifying the frequency at
which <code>name="tsc"</code> runs.
</dd>
<dt><code>mode</code></dt>
<dd>
The <code>mode</code> attribute controls how
the <code>name="tsc"</code> timer is managed, and can be
"auto", "native", "emulate", "paravirt", or "smpsafe".
Other timers are always emulated.
</dd>
<dt><code>present</code></dt>
<dd>
The <code>present</code> attribute can be "yes" or "no" to
specify whether a particular timer is available to the guest.
</dd>
</dl>
</dd>
</dl>
<h3><a name="elementsDevices">Devices</a></h3>