While developing memory hotplug support in QEMU for PoweKVM, I
realized that guest kernel has specific checks to prevent hot addition
of memory to a memory-less node.
I am referring to arch/powerpc/mm/numa.c:hot_add_scn_to_nid() which
has explicit checks to ensure that it returns a nid that has some some
memory (NODE_DATA(nid)->node_spanned_pages) even when user wants to
hotplug to a node that currently has zero memory.
Is this limitation by design ?