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. Makes sense? -- Kirill A. Shutemov
