On Mon, Oct 26, 2020 at 01:13:52AM +0000, Edgecombe, Rick P wrote: > On Sun, 2020-10-25 at 12:15 +0200, Mike Rapoport wrote: > > Indeed, for architectures that define CONFIG_ARCH_HAS_SET_DIRECT_MAP > > it is > > possible that __kernel_map_pages() would fail, but since this > > function is > > void, the failure will go unnoticed. > > Could you elaborate on how this could happen? Do you mean during > runtime today or if something new was introduced? A failure in__kernel_map_pages() may happen today. For instance, on x86 if the kernel is built with DEBUG_PAGEALLOC. __kernel_map_pages(page, 1, 0); will need to split, say, 2M page and during the split an allocation of page table could fail. Currently, the only user of __kernel_map_pages() outside DEBUG_PAGEALLOC is hibernation, but I think it would be safer to entirely prevent usage of __kernel_map_pages() when DEBUG_PAGEALLOC=n. -- Sincerely yours, Mike.
