Node 0 not necessary for powerpc?

[Christoph Lameter]

On Mon, 19 May 2014, Nishanth Aravamudan wrote:

> I'm seeing a panic at boot with this change on an LPAR which actually
> has no Node 0. Here's what I think is happening:
>
> start_kernel
>     ...
>     -> setup_per_cpu_areas
>         -> pcpu_embed_first_chunk
>             -> pcpu_fc_alloc
>                 -> ___alloc_bootmem_node(NODE_DATA(cpu_to_node(cpu), ...
>     -> smp_prepare_boot_cpu
>         -> set_numa_node(boot_cpuid)
>
> So we panic on the NODE_DATA call. It seems that ia64, at least, uses
> pcpu_alloc_first_chunk rather than embed. x86 has some code to handle
> early calls of cpu_to_node (early_cpu_to_node) and sets the mapping for
> all CPUs in setup_per_cpu_areas().

Maybe we can switch ia64 too embed? Tejun: Why are there these
dependencies?

> Thoughts? Does that mean we need something similar to x86 for powerpc?

Tejun is the expert in this area. CCing him.