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

Peter Krempa pkrempa at redhat.com
Mon Feb 25 09:08:50 UTC 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




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