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

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.