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Re: [Qemu-devel] QMP event for suspend to disk
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] QMP event for suspend to disk |
Date: |
Wed, 18 Jul 2012 08:17:48 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120615 Thunderbird/13.0.1 |
On 07/18/2012 08:02 AM, Luiz Capitulino wrote:
> Hi,
>
> QEMU can now distinguish between S4 and power off for the guest OSes that
> suspends to disk through S4. This means that we can have a QMP event for S4
> (so that QMP clients can distinguish between S3 and S4).
>
> However, as we already emit the SHUTDOWN event for this, it turns out that
> there are three different ways of supporting the new event. We could:
>
> 1. not emit the SHUTDOWN event and only emit the SUSPEND_DISK event
>
> cons: breaks compatibility, as we'll stop sending an event we send today.
At least the new 'query-events' monitor command will allow libvirt to
know which events to listen for; so this is workable.
>
> 2. emit both, that is, first SUSPEND_DISK and then SHUTDOWN
>
> cons: emitting two very similar events.
This has the most back-compat, but is noisier in that it generates more
events.
>
> 3. extend the SHUTDOWN event to say whether it's a suspend to disk or not,
> like this:
>
> { "event": "SHUTDOWN", "data": { "suspend-to-disk": true }, ... }
>
> cons: we already have the SUSPEND event, so from an API perspective
> it would make sense to have SUSPEND_DISK.
>
> I prefer item 3, because it seems to be cleanest one.
I'm also liking 3, then 1, then 2; but think any of them will work from
libvirt's POV.
--
Eric Blake address@hidden +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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