On Tue, Apr 17, 2018 at 04:13:34PM +0200, Markus Armbruster wrote: > Igor Mammedov <imamm...@redhat.com> writes: > > [...] > > Series allows to configure NUMA mapping at runtime using QMP > > interface. For that to happen it introduces a new '-preconfig' CLI option > > which allows to pause QEMU before machine_init() is run and > > adds new set-numa-node QMP command which in conjunction with > > query-hotpluggable-cpus allows to configure NUMA mapping for cpus. > > > > Later we can modify other commands to run early, for example device_add. > > I recall SPAPR had problem when libvirt started QEMU with -S and, while it's > > paused, added CPUs with device_add. Intent was to coldplug CPUs (but at that > > stage it's considered hotplug already), so SPAPR had to work around the > > issue. > > That instance is just stupidity / laziness, I think: we consider any > plug after machine creation a hot plug. Real machines remain cold until > you press the power button. Our virtual machines should remain cold > until they start running, i.e. with -S until the first "cont". > > I vaguely remember me asking this before, but your answer didn't make it > into this cover letter, which gives me a pretext to ask again instead of > looking it up in the archives: what exactly prevents us from keeping the > machine cold enough for numa configuration until the first "cont"?
I also think this would be better, but it seems to be difficult in practice, see: http://mid.mail-archive.com/20180323210532.GD28161@localhost.localdomain -- Eduardo