These questions got raised while I was going through vm_normal_page - 1) Why are there some special pte_mappings? [when i went through mm/memory.c, ] 2) why is [is_zero_pfn] zero pfn used? I followed the code path, but could not understand semantically what is a special pte mapping used for and this zer_pfn? It would be great if you can please point me to resources. Thanks !