Re: virtagent for qemu-kvm ?

[Michael Roth <mdroth@linux.vnet.ibm.com>]

On 07/26/2011 03:24 AM, Stefan Hajnoczi wrote:
> On Tue, Jul 26, 2011 at 6:58 AM, Prateek Sharma<prateeks@cse.iitb.ac.in>  wrote:
>> On Tue, 26 Jul 2011, Stefan Hajnoczi wrote:
>>
>>> On Tue, Jul 26, 2011 at 6:05 AM, Prateek Sharma<prateeks@cse.iitb.ac.in>
>>> wrote:
>>>>
>>>> Hi all,
>>>>     Is there any equivalent of qemu's virtagent in qemu-kvm?
>>>> [http://lists.gnu.org/archive/html/qemu-devel/2011-01/msg02149.html]  .
>>>> In particular , i want to share pages between KVM guests and the host .
>>>> Is
>>>> there an appropriate mechanism for this in existence which i could use ?
>>>> Another nice feature virtagent provides is the ability to see guest dmesg
>>>> output in the host...
>>>
>>> virtagent doesn't share pages between guest and host AFAIK.
>>>
>>> Have you looked at hw/ivshmem.c?
>>>
>>> Most of the time you don't need to actually share pages between guest
>>> and host.  Use existing mechanisms like networking or serial to
>>> communicate instead.
>>>
>>> Stefan
>>>
>>
>> Thanks for the quick response!
>>
>> I was tempted by virtagent because it provides dmesg output directly,
>> something which is exactly what i need.
>>
>> Anyway, looks like i'll need to fallback to serial/networking, as you
>> suggested.
>>
>> On a related note, is porting virtagent to qemu-kvm
>> possible/useful/in-the-pipeline ?
>
> I expect qemu-ga will be merged into qemu-kvm.git when they merge from
> qemu.git again soon.
>
> Mike: I don't see a dmesg command in the guest schema in qemu.git.  Is
> there a recommended way of getting dmesg from the host (maybe read
> file /var/log/messages)?
>

Yup, the guest-file-read RPC to access /var/log/messages is the only 
means in the current version. There was a dmesg RPC in earlier 
prototypes but it was removed in favor of lower-level mechanisms.

> Stefan