Re: [PATCH 6/7] mm: convert generic code to 5-level paging
From: Michal Hocko
Date: Wed Mar 08 2017 - 08:59:36 EST
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.
Other than that free to to add
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
The rest of the series look good (as good as all the pte hackery can get
;)) as well.
[...]
> diff --git a/mm/kasan/kasan_init.c b/mm/kasan/kasan_init.c
> index 31238dad85fb..7870ad44ee20 100644
> --- a/mm/kasan/kasan_init.c
> +++ b/mm/kasan/kasan_init.c
> @@ -30,6 +30,9 @@
> */
> unsigned char kasan_zero_page[PAGE_SIZE] __page_aligned_bss;
>
> +#if CONFIG_PGTABLE_LEVELS > 4
> +p4d_t kasan_zero_p4d[PTRS_PER_P4D] __page_aligned_bss;
> +#endif
> #if CONFIG_PGTABLE_LEVELS > 3
> pud_t kasan_zero_pud[PTRS_PER_PUD] __page_aligned_bss;
> #endif
[...]
> @@ -136,8 +157,12 @@ void __init kasan_populate_zero_shadow(const void *shadow_start,
> * puds,pmds, so pgd_populate(), pud_populate()
> * is noops.
> */
> - pgd_populate(&init_mm, pgd, lm_alias(kasan_zero_pud));
> - pud = pud_offset(pgd, addr);
> +#ifndef __ARCH_HAS_5LEVEL_HACK
> + pgd_populate(&init_mm, pgd, lm_alias(kasan_zero_p4d));
> +#endif
> + p4d = p4d_offset(pgd, addr);
> + p4d_populate(&init_mm, p4d, lm_alias(kasan_zero_pud));
> + pud = pud_offset(p4d, addr);
> pud_populate(&init_mm, pud, lm_alias(kasan_zero_pmd));
> pmd = pmd_offset(pud, addr);
> pmd_populate_kernel(&init_mm, pmd, lm_alias(kasan_zero_pte));
--
Michal Hocko
SUSE Labs