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Date: Tue, 08 Mar 2011 09:03:45 -0600
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: Re: [Qemu-devel] [PATCH 00/22] QAPI Round 1
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To: Avi Kivity <avi@redhat.com>
Cc: Stefan Hajnoczi <stefanha@gmail.com>, qemu-devel@nongnu.org, Luiz Capitulino <lcapitulino@redhat.com>, Michael D Roth <mdroth@us.ibm.com>, Adam Litke <agl@us.ibm.com>, Markus Armbruster <armbru@redhat.com>

On 03/08/2011 08:52 AM, Avi Kivity wrote:
> On 03/08/2011 04:38 PM, Anthony Liguori wrote:
>>
>> http://wiki.qemu.org/Features/QAPI/GuestAgent
>>
>
> Nice.  A couple of remarks.
>
> We may want to use a different way of separating the namespaces - 
> enacapsulation:
>
> {
>   'command': 'guest-command',
>    arguments: {
>      'command': 'read-file',
>      'arguments': {
>          'path': '/var/log/messages'
>      }
>   }
> }
>
> This serves to decouple the two protocols, which may have different 
> support lifetimes (hopefully not).

We could also have a more proper namespace in the protocol.  Like:

{ 'execute': { 'namespace': 'guest', 'command': 'read-file' }, 
'arguments': { 'path': '/var/log/messages' } }

I'm not sure I see this as all that critical though.  I sort of like the 
idea of it being transparent to the client whether a guest agent 
implements a command or QEMU does.

> In addition to commands we may also implement a key-value store.  A 
> large number of commands may be easy to implement using a single 
> key/value, and it's also easy to live migrate (key/values being stored 
> in but not understood by qemu).

Do you mean the guest querying QEMU for key-values?  QMP doesn't have a 
reverse direction RPC.  It only has events which is one of the things 
that makes live migration work nicely.

Regards,

Anthony Liguori