Re: qemu device model question

[Ian Campbell <ian.campbell@citrix.com>]

On Wed, 2015-05-13 at 10:54 +0200, Juergen Gross wrote:
> Hi,
> 
> while trying to build a pvusb backend in qemu I think I've found a
> general issue in xl: qemu for pv-domains is started only at domain
> creation and only if there is at least one backend in qemu required.
> 
> If there is no qemu process started for the domain at creation time
> it will be impossible to successfully add such a device later while
> the domain is running.
> 
> Are there any plans to remove that restriction? Or have I missed
> some mechanism in xl to start qemu at a later time?

I think it would be reasonable to have some way to indicate that pvusb
support is desired even if there are no such devices on boot, and for
libxl to start the necessary backend in that case.

s/pvusb/whatever/

> Related to this problem is the question whether it would be desirable
> to have e.g. qdisk and pvusb backends in the same process possibly
> influencing each others throughput.

Dissagregation of qemu's PV functionality would be nice, but I'm not
sure how easy/hard it would be.

Ian.