Re: [PATCH mm-unstable] arch, mm: consolidate empty_zero_page

Christophe Leroy (CS GROUP)
2026-01-24T10:16:02Z

Le 24/01/2026 à 10:56, Mike Rapoport a écrit :
> From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
>
> Reduce 22 declarations of empty_zero_page to 3 and 23 declarations of
> ZERO_PAGE() to 4.
>
> Every architecture defines empty_zero_page that way or another, but for the
> most of them it is always a page aligned page in BSS and most definitions
> of ZERO_PAGE do virt_to_page(empty_zero_page).
>
> Move Linus vetted x86 definition of empty_zero_page and ZERO_PAGE() to the
> core MM and drop these definitions in architectures that do not implement
> colored zero page (MIPS and s390).
>
> ZERO_PAGE() remains a macro because turning it to a wrapper for a static
> inline causes severe pain in header dependencies.
>
> For the most part the change is mechanical, with these being noteworthy:
>
> * alpha: aliased empty_zero_page with ZERO_PGE that was also used for boot
> parameters. Switching to a generic empty_zero_page removes the aliasing
> and keeps ZERO_PGE for boot parameters only
> * arm64: uses __pa_symbol() in ZERO_PAGE() so that definition of
> ZERO_PAGE() is kept intact.
> * m68k/parisc/sparc64/um: allocated empty_zero_page from memblock,
> although they do not support zero page coloring and having it in BSS
> will work fine.
> * sh: used empty_zero_page for boot parameters at the very early boot.
> Rename the parameters page to boot_params_page and let sh use the generic
> empty_zero_page.
> * hexagon: had an amusing comment about empty_zero_page
>
> /* A handy thing to have if one has the RAM. Declared in head.S */
>
> that unfortunately had to go :)
>
> Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> ---
> arch/alpha/include/asm/pgtable.h | 6 ------
> arch/arc/include/asm/pgtable.h | 3 ---
> arch/arc/mm/init.c | 2 --
> arch/arm/include/asm/pgtable.h | 9 ---------
> arch/arm/mm/mmu.c | 7 -------
> arch/arm/mm/nommu.c | 7 -------
> arch/arm64/include/asm/pgtable.h | 1 -
> arch/arm64/mm/mmu.c | 7 -------
> arch/csky/include/asm/pgtable.h | 3 ---
> arch/csky/mm/init.c | 3 ---
> arch/hexagon/include/asm/pgtable.h | 6 ------
> arch/hexagon/kernel/head.S | 5 -----
> arch/hexagon/kernel/hexagon_ksyms.c | 1 -
> arch/loongarch/include/asm/pgtable.h | 9 ---------
> arch/loongarch/mm/init.c | 3 ---
> arch/m68k/include/asm/pgtable_mm.h | 9 ---------
> arch/m68k/include/asm/pgtable_no.h | 7 -------
> arch/m68k/mm/init.c | 9 ---------
> arch/m68k/mm/mcfmmu.c | 2 --
> arch/m68k/mm/motorola.c | 6 ------
> arch/m68k/mm/sun3mmu.c | 2 --
> arch/microblaze/include/asm/pgtable.h | 10 ----------
> arch/microblaze/kernel/head.S | 4 ----
> arch/microblaze/kernel/microblaze_ksyms.c | 2 --
> arch/nios2/include/asm/pgtable.h | 7 -------
> arch/nios2/kernel/head.S | 10 ----------
> arch/nios2/kernel/nios2_ksyms.c | 1 -
> arch/openrisc/include/asm/pgtable.h | 4 ----
> arch/openrisc/kernel/head.S | 3 ---
> arch/openrisc/kernel/or32_ksyms.c | 1 -
> arch/openrisc/mm/init.c | 3 ---
> arch/parisc/include/asm/pgtable.h | 11 -----------
> arch/parisc/mm/init.c | 6 ------
> arch/powerpc/include/asm/pgtable.h | 6 ------
> arch/powerpc/mm/mem.c | 3 ---

For powerpc:

Reviewed-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>

> arch/riscv/include/asm/pgtable.h | 7 -------
> arch/riscv/mm/init.c | 4 ----
> arch/sh/include/asm/pgtable.h | 8 --------
> arch/sh/include/asm/setup.h | 3 ++-
> arch/sh/kernel/head_32.S | 4 ++--
> arch/sh/kernel/sh_ksyms_32.c | 1 -
> arch/sh/mm/init.c | 1 -
> arch/sparc/include/asm/pgtable_32.h | 8 --------
> arch/sparc/include/asm/pgtable_64.h | 3 ---
> arch/sparc/include/asm/setup.h | 2 --
> arch/sparc/kernel/head_32.S | 7 -------
> arch/sparc/mm/init_32.c | 4 ----
> arch/sparc/mm/init_64.c | 15 ---------------
> arch/um/include/asm/pgtable.h | 9 ---------
> arch/um/include/shared/kern_util.h | 1 -
> arch/um/kernel/mem.c | 16 ----------------
> arch/um/kernel/um_arch.c | 1 -
> arch/x86/include/asm/pgtable.h | 8 --------
> arch/x86/kernel/head_32.S | 4 ----
> arch/x86/kernel/head_64.S | 7 -------
> arch/xtensa/include/asm/pgtable.h | 4 ----
> arch/xtensa/kernel/head.S | 3 ---
> arch/xtensa/kernel/xtensa_ksyms.c | 2 --
> include/linux/pgtable.h | 8 ++++++++
> mm/mm_init.c | 9 +++++++++
> 60 files changed, 21 insertions(+), 296 deletions(-)
>