Re: [PATCH v13 06/14] mm: HUGE_VMAP arch support cleanup

[Christophe Leroy]

Le 28/04/2021 à 10:32, Christophe Leroy a écrit :
> Le 17/03/2021 à 07:23, Nicholas Piggin a écrit :
> > This changes the awkward approach where architectures provide init
> > functions to determine which levels they can provide large mappings for,
> > to one where the arch is queried for each call.
> >
> > This removes code and indirection, and allows constant-folding of dead
> > code for unsupported levels.
> >
> > This also adds a prot argument to the arch query. This is unused
> > currently but could help with some architectures (e.g., some powerpc
> > processors can't map uncacheable memory with large pages).
> >
> > Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
> > Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> > Cc: Will Deacon <will@xxxxxxxxxx>
> > Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> > Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> > Cc: Borislav Petkov <bp@xxxxxxxxx>
> > Cc: x86@xxxxxxxxxx
> > Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
> > Reviewed-by: Ding Tianhong <dingtianhong@xxxxxxxxxx>
> > Acked-by: Catalin Marinas <catalin.marinas@xxxxxxx> [arm64]
> > Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx>
> > ---
> >   arch/arm64/include/asm/vmalloc.h         |  8 ++
> >   arch/arm64/mm/mmu.c                      | 10 +--
> >   arch/powerpc/include/asm/vmalloc.h       |  8 ++
> >   arch/powerpc/mm/book3s64/radix_pgtable.c |  8 +-
> >   arch/x86/include/asm/vmalloc.h           |  7 ++
> >   arch/x86/mm/ioremap.c                    | 12 +--
> >   include/linux/io.h                       |  9 ---
> >   include/linux/vmalloc.h                  |  6 ++
> >   init/main.c                              |  1 -
> >   mm/debug_vm_pgtable.c                    |  4 +-
> >   mm/ioremap.c                             | 94 ++++++++++--------------
> >   11 files changed, 87 insertions(+), 80 deletions(-)
>
> > diff --git a/mm/ioremap.c b/mm/ioremap.c
> > index 3f4d36f9745a..3264d0203785 100644
> > --- a/mm/ioremap.c
> > +++ b/mm/ioremap.c
> > @@ -16,49 +16,16 @@
> >   #include "pgalloc-track.h"
> >   #ifdef CONFIG_HAVE_ARCH_HUGE_VMAP
> > -static int __read_mostly ioremap_p4d_capable;
> > -static int __read_mostly ioremap_pud_capable;
> > -static int __read_mostly ioremap_pmd_capable;
> > -static int __read_mostly ioremap_huge_disabled;
> > +static bool __ro_after_init iomap_max_page_shift = PAGE_SHIFT;
>
> Must be an int, not a bool.

And the initial value seems wrong. Should be P4D_SHIFT ?

> >   static int __init set_nohugeiomap(char *str)
> >   {
> > -    ioremap_huge_disabled = 1;
> > +    iomap_max_page_shift = P4D_SHIFT;

And PAGE_SHIFT here when NO hugeiomap ?

> >       return 0;
> >   }
> >   early_param("nohugeiomap", set_nohugeiomap);

Christophe