Comment 4 for bug 1677552

------- Comment From <email address hidden> 2017-03-30 09:24 EDT-------
(In reply to comment #17)
> I agree to your statement: "So the fix for this is to get Jianjun's DRC
> migration patchset upstream and then to 1704".
>
> I checked and found that this has some pretty long history [1].
> I looked at the context but you are so much more aware of the details that I
> have some questions for you below.
>
> You wrote you tested v5 which I found is the last one before v6 stated to:
> "Split from Power specific patches". I guess you mean you tried [2] then
> right?

Right, I tried with ppc specific patches from [2] on mainline QEMU which already has QTAILQ bits in it.

>
> I didn't find the future of the ppc part after v6. The diffstat changed
> tremendously v5 -> v6.. Is the ppc specific code no more needed in the newer
> revisions, or was it just dropped (or ppc parts even accepted already) to
> get some better progress on the generic content first?

Yes, I think so.

>
> The cover letter text always states about "spapr DRC state" (also RTAS)
> which sounds very PPC specific, yet the last revisions seemed to be more
> generic - but maybe only to implement the tailq bits in general. Do you
> happen to know if the negative effect is
> a) only affecting ppc (I know x86 has no perfect hotplug history anyway)?

Yes, this affects only hotplug on PPC.

> b) a regression that worked with old versions (maybe because libvirt did
> start qemu differently as you outlined)?

This is not a regression for CPU hotplug because this situation never worked right from the beginning.

>
> I found that the latter v17 was queued and pulled in [3].
> Changes are in v2.9.0-rc0 and later, does that now mean all you need is in
> 2.9?
> Or are the ppc changes that got split v5->v6 still missing and need to be
> rebased on top on what went upstream with v17 just recently?

2.9 has the generic changes (QTAILQ migration) in, but PPC bits (DRC state migration) yet need to be upstreamed first.

Jianjun is working on this and he will be upstreaming the PPC bits soon. However I don't think we have enough time to get his changes into 2.9 now.