[Patch 2/2]: powerpc/hotplug/mm: Fix hot-add memory node assoc

[Michael Ellerman]

Reza Arbab <arbab at linux.vnet.ibm.com> writes:

> On Thu, May 25, 2017 at 04:19:53PM +1000, Michael Ellerman wrote:
>>The commit message for 3af229f2071f says:
>>
>>    In practice, we never see a system with 256 NUMA nodes, and in fact, we
>>    do not support node hotplug on power in the first place, so the nodes
>>    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>    that are online when we come up are the nodes that will be present for
>>    the lifetime of this kernel.
>>
>>Is that no longer true?
>
> I don't know what the reasoning behind that statement was at the time, 
> but as far as I can tell, the only thing missing for node hotplug now is 
> Balbir's patchset [1]. He fixes the resource issue which motivated 
> 3af229f2071f and reverts it.
>
> With that set, I can instantiate a new numa node just by doing 
> add_memory(nid, ...) where nid doesn't currently exist.

But does that actually happen on any real system?

cheers