Re: [PATCH v10 05/12] mm: HUGE_VMAP arch support cleanup

Christophe Leroy
2021-01-25T08:41:01Z

Le 24/01/2021 à 09:22, 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.

It looks like this is only the case when CONFIG_HAVE_ARCH_HUGE_VMAP is not defined.

When it is defined, for exemple on powerpc you defined arch_vmap_p4d_supported() as a regular
function in arch/powerpc/mm/book3s64/radix_pgtable.c, so allthough it returns always false, it won't
constant fold dead code.

>
> 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@lists.ozlabs.org
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: x86@kernel.org
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Acked-by: Catalin Marinas <catalin.marinas@arm.com> [arm64]
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> ---
> 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/ioremap.c | 88 +++++++++---------------
> 10 files changed, 79 insertions(+), 78 deletions(-)
>

Christophe