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

[Michael Ellerman]

Michael Bringmann <mwb@xxxxxxxxxxxxxxxxxx> writes:

> On 05/24/2017 06:19 AM, Michael Ellerman wrote:
>> Michael Bringmann <mwb@xxxxxxxxxxxxxxxxxx> writes:
>>>
>>> With or without 3af229f2071f, we would still need to add something, somewhere to add new
>>> bits to the 'node_possible_map'.  That is not being done.
>> 
>> You mustn't add bits to the possible map after boot.
>> 
>> That's its purpose, to tell you what nodes could ever *possibly* exist.
>
> The problem that I have been encountering is that the 'possible map' did *not*
> show all of the possible nodes.

OK so how did that happen?

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?

cheers