On Wed, Jul 20, 2016 at 09:01:11AM +0200, Peter Krempa wrote: > On Wed, Jul 20, 2016 at 11:00:05 +1000, David Gibson wrote: > > On Tue, Jul 19, 2016 at 01:52:40PM +0200, Peter Krempa wrote: > > > On Mon, Jul 18, 2016 at 19:19:19 +1000, David Gibson wrote: > > > > The spapr implementation of query-hotpluggable-cpus builds the list of > > > > hotpluggable cores from the end (most removed from the list head) > > > > because that's the easiest way with a singly linked list. Because it > > > > also traverses the possible CPU cores starting from low indexes the > > > > resulting list has the cpu cores listed in reverse order by core-id. > > > > > > > > That's not generally harmful, but it means the output from "info > > > > hotpluggable-cpus" is a little harder to read than it could be. > > > > > > > > Therefore, traverse the cpus in reverse order so that the final list > > > > ends up in increasing-core-id order. > > > > > > To make this interface usable with in-order hotplug the ordering of the > > > entries should be codified in the schema documentation. (see my response > > > on the cover letter for justification). > > > > I'm not really sure what you mean by this. > > Currently the order of entries in reply of query-hotpluggable-cpus is > arbitrary as this patch hints. > > If qemu won't support arbitrary order hotplug but libvirt should be able > to use the new interface, then the order of replies of > query-hotpluggable-cpus need to corelate (in a documented fashion) with > the order we need to plug the cpus in. By not documenting any order > libvirt can just guess it (by reimplementing the algorithm in qemu). > > I've pointed this out in a sub-thread of the cover-letter.
So, based on Peter's comments (and others) I've concluded that the
cpu-add implementation in terms of the new interface isn't really
useful.
However, I think this re-ordering is still a good idea, because:
* It makes info hotpluggable-cpus easier to read in the HMP
* Although we certainly need a better approach to handling hotplug +
NUMA, correcting the order should allow the existing NUMA
interface to work with only as much guesswork in libvirt as we
already have.
* We haven't released a qemu with query-hotpluggable-cpus yet, so we
shouldn't need version conditions in order to use the order.
For that reason I've tentatively merged this patch into ppc-for-2.7.
It would be good to get an R-b or A-b from someone before I send a
pull request (which I'm hoping to do tomorrow).
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
signature.asc
Description: PGP signature
