Subject: Re: [PATCH v2] powerpc/numa: set node_possible_map to only node_online_map during boot

From: Michael Ellerman <[email-masked]>
Date: Tue, 10 Mar 2015 10:55:05 +1100

On Thu, 2015-03-05 at 21:27 -0800, Nishanth Aravamudan wrote:
> diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
> index 0257a7d659ef..0c1716cd271f 100644
> --- a/arch/powerpc/mm/numa.c
> +++ b/arch/powerpc/mm/numa.c
> @@ -958,6 +958,13 @@ void __init initmem_init(void)
>  
>  	memblock_dump_all();
>  
> +	/*
> +	 * Reduce the possible NUMA nodes to the online NUMA nodes,
> +	 * since we do not support node hotplug. This ensures that  we
> +	 * lower the maximum NUMA node ID to what is actually present.
> +	 */
> +	node_possible_map = node_online_map;

That looks nice, but is it generating what we want?

ie. is the content of node_online_map being *copied* into node_possible_map.

Or are we changing node_possible_map to point at node_online_map?

cheers