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

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:

In the current model, only one instance of qemu is running for each running HVM

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.


Anthony Liguori

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