vmemmap_p4d_populate
p4d = vmemmap_p4d_populate(pgd, vstart, node);
p4d_t *vmemmap_p4d_populate(pgd_t *pgd, unsigned long addr, int node);
p4d = vmemmap_p4d_populate(pgd, addr, node);
p4d = vmemmap_p4d_populate(pgd, addr, node);