Re: [libvirt] [PATCH] libvirt: qemu: Fix domain termination caused by query-hotpluggable-cpus not enabled

On Fri, Nov 25, 2016 at 14:25:33 +0100, Boris Fiuczynski wrote: In the global capabilities cache, the QEMU_CAPS_QUERY_HOTPLUGGABLE_CPUS is set if the command is supported by qemu. Once a VM is started we create a copy of the given capability set and possibly filter out stuff that won't work and then store the filtered capability set in the domain object. No. You can't do that at reconnect time. Once you start the VM you can completely replace the original binary and thus you don't have data that would allow to do such operation at reconnect time. That is the main reason why we store the capabilities in the status XML rather than reloading it from the cache. Yes, exactly. As said, the capability set should not be re-detected for the reasons stated above. Said the above, there's something fishy going on. I compiled a qemu binary that specifically doesn't support cpu hotplug and started a VM. The status XML file does not show the flag: # grep query-hotpluggable-cpus /var/run/libvirt/qemu/upstream.xml # But an attempt to restart libvirtd indeed ends up in the VM being killed: 016-11-25 14:09:12.909+0000: 2610599: error : qemuMonitorJSONCheckError:387 : internal error: unable to execute QEMU command 'query-hotpluggable-cpus': The feature 'query-hotpluggable-cpus' is not enabled This means that the capabilities are not properly restored. Peter