Re: [PATCH v2 00/28] arch, mm: consolidate hugetlb early reservation

[Frank van der Linden <fvdl@google.com>]

On Thu, Jan 1, 2026 at 11:00 PM Mike Rapoport <rppt@kernel.org> wrote:
>
> From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
>
> Hi,
>
> Order in which early memory reservation for hugetlb happens depends on
> architecture, on configuration options and on command line parameters.
>
> Some architectures rely on the core MM to call hugetlb_bootmem_alloc()
> while others call it very early to allow pre-allocation of HVO-style
> vmemmap.
>
> When hugetlb_cma is supported by an architecture it is initialized during
> setup_arch() and then later hugetlb_init code needs to understand did it
> happen or not.
>
> To make everything consistent and unified, both reservation of hugetlb
> memory from bootmem and creation of CMA areas for hugetlb must be called
> from core MM initialization and it would have been a simple change.
> However, HVO-style pre-initialization ordering requirements slightly
> complicate things and for HVO pre-init to work sparse and memory map should
> be initialized after hugetlb reservations.
>
> This required pulling out the call to free_area_init() out of setup_arch()
> path and moving it MM initialization and this is what the first 23 patches
> do.
>
> These changes are deliberately split into per-arch patches that change how
> the zone limits are calculated for each architecture and the patches 22 and
> 23 just remove the calls to free_area_init() and sprase_init() from arch/*.
>
> Patch 24 is a simple cleanup for MIPS.
>
> Patches 25 and 26 actually consolidate hugetlb reservations and patches 27
> and 28 perform some aftermath cleanups.
>
> I tried to trim the distribution list and although it's still quite long
> if you feel that someone was wrongly excluded please add them back.
>
> The changes also available in git:
> https://git.kernel.org/pub/scm/linux/kernel/git/rppt/linux.git/log/?h=hugetlb-init/v2
>
> v2 changes:
> * move the hugetlb and memory map initializaion to mm_core_init_early()
> * add Acks
>
> v1: https://lore.kernel.org/all/20251228124001.3624742-1-rppt@kernel.org
>
> Mike Rapoport (Microsoft) (28):
>   alpha: introduce arch_zone_limits_init()
>   arc: introduce arch_zone_limits_init()
>   arm: introduce arch_zone_limits_init()
>   arm64: introduce arch_zone_limits_init()
>   csky: introduce arch_zone_limits_init()
>   hexagon: introduce arch_zone_limits_init()
>   loongarch: introduce arch_zone_limits_init()
>   m68k: introduce arch_zone_limits_init()
>   microblaze: introduce arch_zone_limits_init()
>   mips: introduce arch_zone_limits_init()
>   nios2: introduce arch_zone_limits_init()
>   openrisc: introduce arch_zone_limits_init()
>   parisc: introduce arch_zone_limits_init()
>   powerpc: introduce arch_zone_limits_init()
>   riscv: introduce arch_zone_limits_init()
>   s390: introduce arch_zone_limits_init()
>   sh: introduce arch_zone_limits_init()
>   sparc: introduce arch_zone_limits_init()
>   um: introduce arch_zone_limits_init()
>   x86: introduce arch_zone_limits_init()
>   xtensa: introduce arch_zone_limits_init()
>   arch, mm: consolidate initialization of nodes, zones and memory map
>   arch, mm: consolidate initialization of SPARSE memory model
>   mips: drop paging_init()
>   x86: don't reserve hugetlb memory in setup_arch()
>   mm, arch: consolidate hugetlb CMA reservation
>   mm/hugetlb: drop hugetlb_cma_check()
>   Revert "mm/hugetlb: deal with multiple calls to hugetlb_bootmem_alloc"
>
>  .../driver-api/cxl/linux/early-boot.rst       |  2 +-
>  Documentation/mm/memory-model.rst             |  3 --
>  .../translations/zh_CN/mm/memory-model.rst    |  2 -
>  arch/alpha/kernel/setup.c                     |  1 -
>  arch/alpha/mm/init.c                          | 16 ++++----
>  arch/arc/mm/init.c                            | 37 +++++++++---------
>  arch/arm/mm/init.c                            | 25 ++----------
>  arch/arm64/include/asm/hugetlb.h              |  2 -
>  arch/arm64/mm/hugetlbpage.c                   | 10 ++---
>  arch/arm64/mm/init.c                          | 39 ++++++++-----------
>  arch/csky/kernel/setup.c                      | 16 ++++----
>  arch/hexagon/mm/init.c                        | 19 +++------
>  arch/loongarch/include/asm/pgtable.h          |  2 -
>  arch/loongarch/kernel/setup.c                 | 10 -----
>  arch/loongarch/mm/init.c                      |  6 +--
>  arch/m68k/mm/init.c                           |  8 ++--
>  arch/m68k/mm/mcfmmu.c                         |  3 --
>  arch/m68k/mm/motorola.c                       |  6 +--
>  arch/m68k/mm/sun3mmu.c                        |  9 -----
>  arch/microblaze/mm/init.c                     | 22 +++++------
>  arch/mips/include/asm/pgalloc.h               |  2 -
>  arch/mips/include/asm/pgtable.h               |  2 +-
>  arch/mips/kernel/setup.c                      | 15 +------
>  arch/mips/loongson64/numa.c                   | 10 ++---
>  arch/mips/mm/init.c                           |  8 +---
>  arch/mips/sgi-ip27/ip27-memory.c              |  8 +---
>  arch/nios2/mm/init.c                          | 12 +++---
>  arch/openrisc/mm/init.c                       | 10 +----
>  arch/parisc/mm/init.c                         | 11 +-----
>  arch/powerpc/include/asm/hugetlb.h            |  5 ---
>  arch/powerpc/include/asm/setup.h              |  4 ++
>  arch/powerpc/kernel/setup-common.c            |  1 -
>  arch/powerpc/mm/hugetlbpage.c                 | 11 ++----
>  arch/powerpc/mm/mem.c                         | 27 +++++--------
>  arch/powerpc/mm/numa.c                        |  2 -
>  arch/riscv/mm/hugetlbpage.c                   |  8 ++++
>  arch/riscv/mm/init.c                          | 10 +----
>  arch/s390/kernel/setup.c                      |  2 -
>  arch/s390/mm/hugetlbpage.c                    |  8 ++++
>  arch/s390/mm/init.c                           | 13 +++----
>  arch/sh/mm/init.c                             | 12 +++---
>  arch/sparc/mm/init_64.c                       | 17 +++-----
>  arch/sparc/mm/srmmu.c                         | 17 ++++----
>  arch/um/kernel/mem.c                          | 10 ++---
>  arch/x86/kernel/setup.c                       |  5 ---
>  arch/x86/mm/hugetlbpage.c                     |  8 ++++
>  arch/x86/mm/init.c                            |  8 +---
>  arch/x86/mm/init_32.c                         |  2 -
>  arch/x86/mm/init_64.c                         |  4 --
>  arch/x86/mm/mm_internal.h                     |  1 -
>  arch/xtensa/mm/init.c                         | 14 +++----
>  include/linux/hugetlb.h                       | 12 ++----
>  include/linux/mm.h                            |  5 ++-
>  include/linux/mmzone.h                        |  2 -
>  init/main.c                                   |  1 +
>  mm/hugetlb.c                                  | 13 -------
>  mm/hugetlb_cma.c                              | 33 ++++++++--------
>  mm/hugetlb_cma.h                              |  5 ---
>  mm/hugetlb_vmemmap.c                          | 11 ------
>  mm/internal.h                                 |  6 +++
>  mm/mm_init.c                                  | 20 ++++++----
>  61 files changed, 219 insertions(+), 394 deletions(-)
>
>
> base-commit: 8f0b4cce4481fb22653697cced8d0d04027cb1e8
> --
> 2.51.0
>

Thanks for this series. When I introduced HVO pre-init, I noticed the
inconsistencies in init order, but shied away from attempting any
general cleanup, as I had only tested pre-init on x86.

With this, it should be possible to enable
ARCH_WANT_HUGETLB_VMEMMAP_PREINIT on architectures that support HVO. I
think that's only riscv and loongarch right now. But that's out of
scope here, though.

- Frank