On Thu, Mar 09, 2017 at 10:54:15AM +0100, Michal Hocko wrote: > On Wed 08-03-17 18:21:30, Kirill A. Shutemov wrote: > > On Wed, Mar 08, 2017 at 02:57:35PM +0100, Michal Hocko wrote: > > > On Mon 06-03-17 23:45:13, Kirill A. Shutemov wrote: > > > > Convert all non-architecture-specific code to 5-level paging. > > > > > > > > It's mostly mechanical adding handling one more page table level in > > > > places where we deal with pud_t. > > > > > > > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > > > > > > OK, I haven't spotted anything major. I am just scratching my head about > > > the __ARCH_HAS_5LEVEL_HACK leak into kasan_init.c (see below). Why do we > > > need it? It looks more than ugly but I am not familiar with kasan so > > > maybe this is really necessary. > > > > Yeah ugly. > > > > kasan_zero_p4d is only defined if we have real page table level. It's okay > > if the page table level is folded properly -- using pgtable-nop4d.h -- in > > this case pgd_populate() is nop and we don't reference kasan_zero_p4d. > > > > With 5level-fixup.h, pgd_populate() is not nop, so we would reference > > kasan_zero_p4d and build breaks. We don't need this as p4d_populate() > > would do what we really need in this case. > > > > We can drop the hack once all architectures that support kasan would be > > converted to pgtable-nop4d.h -- amd64 and x86 at the moment. > > But those architectures even do not enable kasan > $ git grep "select *HAVE_ARCH_KASAN" > arch/arm64/Kconfig: select HAVE_ARCH_KASAN if SPARSEMEM_VMEMMAP && !(ARM64_16K_PAGES && ARM64_VA_BITS_48) > arch/x86/Kconfig: select HAVE_ARCH_KASAN if X86_64 && SPARSEMEM_VMEMMAP > > both arm64 and x86 (64b) do compile fine without the ifdef... So I guess > we should be fine without it. Have you build the image to the final linking? lm_alias() hides the error until later. x86-64 allmodconfig without the #ifndef: MODPOST vmlinux.o mm/built-in.o: In function `kasan_populate_zero_shadow': (.init.text+0xb72b): undefined reference to `kasan_zero_p4d' Makefile:983: recipe for target 'vmlinux' failed make: *** [vmlinux] Error 1 -- Kirill A. Shutemov -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
