On Wed, Feb 24, 2016 at 03:42:18PM +0100, Igor Mammedov wrote: > On Tue, 23 Feb 2016 18:26:20 -0300 > Eduardo Habkost <ehabk...@redhat.com> wrote: > > > On Tue, Feb 23, 2016 at 10:46:45AM +0100, Igor Mammedov wrote: > > > On Mon, 22 Feb 2016 13:54:32 +1100 > > > David Gibson <da...@gibson.dropbear.id.au> wrote: > > [...] > > > > This is why Eduardo suggested - and I agreed - that it's probably > > > > better to implement the "1st layer" as an internal structure/interface > > > > only, and implement the 2nd layer on top of that. When/if we need to > > > > we can revisit a user-accessible interface to the 1st layer. > > > We are going around QOM based CPU introspecting interface for > > > years now and that's exactly what 2nd layer is, just another > > > implementation. I've just lost hope in this approach. > > > > > > What I'm suggesting in this RFC is to forget controversial > > > QOM approach for now and use -device/device_add + QMP introspection, > > > > You have a point about it looking controversial, but I would like > > to understand why exactly it is controversial. Discussions seem > > to get stuck every single time we try to do something useful with > > the QOM tree, and I don't undertsand why. > Maybe because we are trying to create a universal solution to fit > ALL platforms? And every time some one posts patches to show > implementation, it would break something in existing machine > or is not complete in terms of how interface would work wrt > mgmt/CLI/migration.
That's true. > > > > > > i.e. completely split interface from how boards internally implement > > > CPU hotplug. > > > > A QOM-based interface may still split the interface from how > > boards internally implement CPU hotplug. They don't need to > > affect the device tree of the machine, we just need to create QOM > > objects or links at predictable paths, that implement certain > > interfaces. > Beside of not being able to reach consensus for a long time, > I'm fine with isolated QOM interface if it allow us to move forward. > However static QMP/QAPI interface seems to be better describing and > has better documentation vs current very flexible poorly self-describing QOM. You have a good point: QMP is more stable and better documented. QOM is easier for making experiments, and I would really like to see it being used more. But if we still don't understand the requirements enough to design a QMP interface, we won't be able to implement the same functionality using QOM either. If we figure out the requirements, I believe we should be able to design equivalent QMP and QOM interfaces. -- Eduardo
