[libvirt] [PATCH v3 3/4] qemu_capabilities: Introduce QEMU_CAPS_PM_WAKEUP_SUPPORT

[Daniel Henrique Barboza]

On 4/11/19 8:43 AM, Peter Krempa wrote:
> On Thu, Apr 11, 2019 at 13:37:49 +0200, Michal Privoznik wrote:
>> On 4/11/19 12:12 PM, Daniel Henrique Barboza wrote:
>>> <snip/>
>>>
>>> All that said, I think a good solution would be (2). dompmsuspend isn't a
>>> performance sensitive command, thus the extra time to execute the API
>>> can be ignored. Also, we can still check for
>>> QEMU_CAPS_QUERY_CURRENT_MACHINE
>>> inside qemuDomainPMSuspendForDuration to avoid firing up an error in a
>>> QEMU version that doesn't know the API.
>> That's the thing. We can't. The capability doesn't exist yet. So every
>> domain that is currently running thinks that qemu doesn't have the
>> capability. And when updating libvirt to say next release only freshly
>> started domains might/will have the capability. For all already running
>> domains libvirt thinks the capability is not there. Only freshly started
>> domains will get the capability. IOW, upgrading libvirt won't help you
>> unless you restart your domains (might not want to do that).
> If you just go ahead with the PM suspend in case the capability bit for
> the presence of query-current-machine is not present you just will keep
> the existing behaviour. I think that is perfectly tolerable.
>
> Error should be reported only if query-current-machine is supported and
> it returns false for wakeup-suspend-support. (Obviously also if our caps
> indicate that query-current-machine is supported but returns an error).

I agree with this approach.

Michal, do you agree agree with this? If so, let me know if you plan
to re-spin this series again. Otherwise I can do it.


Thanks,


DHB