Re: [Qemu-devel] Qemu disaggregation in Xen environment

[Anthony Liguori <anthony@codemonkey.ws>]

On 03/05/2012 04:53 PM, Stefano Stabellini wrote:
> On Mon, 5 Mar 2012, Anthony Liguori wrote:
>> On 02/28/2012 05:46 AM, Julien Grall wrote:
>>> Hello,
>>>
>>> In the current model, only one instance of qemu is running for each running HVM
>>> domain.
>>>
>>> We are looking at disaggregating qemu to have, for example, an instance to
>>> emulate only
>>> network controllers, another to emulate block devices, etc...
>>
>> Why would you want to do this?
>
> We are trying to disaggregate QEMU, the same way we do with Linux.
>
> On Xen we can run a Linux guest to drive the network card, another Linux
> guest to drive the SATA controller, another one for the management
> stack, etc. This helps both with scalability and isolation.
>
> In this scenario is only natural that we run a QEMU that only emulates
> a SATA controller in the storage domain, a QEMU that only emulates the
> network card in the network domain and everything else in a stubdom.
>
> What's better than using QEMU as emulator? Using three QEMUs per guest
> as emulators! :-)

My concern is that this moves the Xen use case pretty far from what the typical 
QEMU use case would be (running one emulator per guest).

If it was done in a non-invasive way, maybe it would be acceptable but at a high 
level, I don't see how that's possible.

I almost think you would be better off working to build a second front end 
(reusing the device model, and nothing else) specifically for Xen.

Almost like qemu-io but instead of using the block layer, use the device model.

Regards,

Anthony Liguori

>