Re: [PATCH v3 3/4] arch, mm: consolidate empty_zero_page

David Hildenbrand (Arm)
2026-02-12T09:04:25Z

On 2/11/26 11:31, Mike Rapoport wrote:
> 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/um: allocated empty_zero_page from memblock,
> although they do not support zero page coloring and having it in BSS
> will work fine.
> * sparc64 can have empty_zero_page in BSS rather allocate it, but it
> can't use virt_to_page() for BSS. Keep it's definition of ZERO_PAGE()
> but instead of allocating it, make mem_map_zero point to
> empty_zero_page.
> * 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 :)
>
> Acked-by: Helge Deller <deller@gmx.de> # parisc
> Tested-by: Helge Deller <deller@gmx.de> # parisc
> Reviewed-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
> Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
> Acked-by: Catalin Marinas <catalin.marinas@arm.com>
> Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> ---

Acked-by: David Hildenbrand (Arm) <david@kernel.org>

--
Cheers,

David