Re: [PATCH V6 1/2] powerpc/hotplug: Ensure enough nodes avail for operations

From: Michael Bringmann
Date: Wed Jun 21 2017 - 10:25:20 EST

On 06/21/2017 04:52 AM, Michael Ellerman wrote:
> Michael Bringmann <mwb@xxxxxxxxxxxxxxxxxx> writes:
>> powerpc/hotplug: On systems like PowerPC which allow 'hot-add' of CPU
>> or memory resources, it may occur that the new resources are to be
>> inserted into nodes that were not used for these resources at bootup.
>> In the kernel, any node that is used must be defined and initialized
>> at boot. In order to meet both needs, this patch adds a new kernel
>> command line option (numnodes=<int>) for use by the PowerPC architecture-
> Sorry, that's a hack.

It is an intermediate step pending the provision of the firmware properties
under discussion that were mentioned by Nathan Fontenot last week.

> I thought you were going to use firmware properties to find the set of
> possible nodes. Did that not work?

Inference based on the current set of firmware properties for associativity
is insufficient. That is partly the reason for the properties mentioned by
Nathan last week. The current firmware properties only cover what is known
at boot time. They do not cover expansions from DLPAR / hot-add operations
which can add up to everything else on the system.

> cheers


Michael W. Bringmann
Linux Technology Center
IBM Corporation
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