Re: [libvirt] [PATCHv2 2/8] doc: schema: Add basic documentation for the virtual RNG device support

25 Feb 2013


      On 02/22/13 19:20, Eric Blake wrote:
...
On 02/21/2013 07:47 AM, Peter Krempa wrote:
...
This patch documents XML elements used for (basic) support of virtual
RNG devices.
In the devices section in the domain XML users may specify:
For the default 'random' backend:
   <devices>
     <rng model='virtio'>
       <backend model='random'>/dev/urandom</backend>
     </rng>
   </devices>
For the slightly more advanced EGD backend:
   <devices>
     <rng model='virtio'>
       <backend model='egd' type='udp'>
         <!-- this is a definition of a character device -->
         <source mode='bind' service='1234'/>
         <source mode='connect' host='1.2.3.4' service='1234'/>
         <!-- or other valid character device configuration -->
You don't really allow two <source>; maybe a better layout would be a
strategic comment, such as:
<backend model='egd' type='udp'>
         <!-- this is a definition of a character device -->
         <source mode='bind' service='1234'/>
         <!-- or other valid character device configuration, such as
         <source mode='connect' host='1.2.3.4' service='1234'/>
         -->
...
</backend>
     </rng>
   </devices>
For the planned random daemon/pool:
   <devices>
     <rng model='virtio'>
       <backend model='pool' pool='poolname'>class</backend>
Missing </rng>
...
</devices>
to enable the RNG device for guests.
---
Notes:
     Version 2:
     - ACKed, no change, unfortunately doesn't make sense to push alone
Still some nits to fix before pushing:
...
+<pre>
+  ...
+  <devices>
+    <rng model='virtio'>
+      <backend model='random'>/dev/random</backend>
+      <!-- OR -->
+      <backend model='egd' type='udp'>
+        <source mode='bind' service='1234'>
+        <source mode='connect' host='1.2.3.4' service='1234'>
+      </backend>
+    </rng>
+  </devices>
+  ...
Do we really want two <source> in a single <backend> in the example, or
would it be easier to show multiple <rng> devices, one for each type of
backend?
That actually is valid for the character device backends. The UDP 
backend has to use two separate sources for bi-directional 
communication. The definition of that source type is declared as a type 
in our RNG schema an I merely reused that.
...
...
+      <dd>
+        <p>
+          The <code>backend</code> element specifies the source of entropy
+          to be used for the doimain. The source model is configured using the
s/doimain/domain/
...
+          <code>model</code> attribute. Supported source models are:
+        </p>
+        <ul>
+          <li>'random' — /dev/random (default) or similar device as source</li>
+          <li>'egd' — a EGD protocol backend. </li>
not consistent on whether your <li> end with '.'
Peter