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. -- Michal Hocko SUSE Labs
