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Re: [libvirt] [PATCH] Ignore qemu STOP event when stopping CPUs

On Tue, 27 Apr 2010 11:20:39 +0200
jdenemar redhat com wrote:

> From: Jiri Denemark <jdenemar redhat com>
> With JSON qemu monitor, we get a STOP event from qemu whenever qemu
> stops guests CPUs. The downside of it is that vm->state is changed to
> PAUSED and a new generic paused event is send to applications. However,
> when we ask qemu to stop the CPUs we are not really interested in qemu
> event and we usually want to issue a more specific event.

 Can you give an example? Say, "guest is suspended"?

 If this is the case, something you have to consider is whether libvirt
should add high-level events on top of low-level ones.

 Or, to make it more general, what should libvirt report to applications
wrt events?

> By setting vm->status to PAUSED before actually sending the request to
> qemu (and resetting it back if the request fails) we can ignore the
> event since the event handler does nothing when the guest is already
> paused. This solution is quite hacky but unfortunately it's the best
> solution which I was able to come up with and it doesn't introduce a
> race condition.

 You could extend the low-level driver to accept a mask of events to
be ignored.

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