Re: [PATCH 0/6] arm64: distinguish HW PTE pointers from SW PTE value pointers

[Ryan Roberts <ryan.roberts@arm.com>]

On 14/09/2026 14:51, Muhammad Usama Anjum wrote:
> Hi,
> 
> The generic series introduces hw_pte_t for HW PTEs, while SW PTE values
> use pte_t. This series enables the distinct type on arm64 so the
> compiler can distinguish HW PTE pointers (hw_pte_t *) from SW PTE value
> pointers (pte_t *).
> 
> The conversion updates HW PTE pointers and accessors, including atomic
> updates, fixmap, and early page-table construction, before selecting
> ARCH_HAS_HW_PTE_T. Higher-level entry types remain out of scope, and
> shared helpers retain explicit casts.
> 
> The linked generic series is a prerequisite. Its cover contains the
> Coccinelle script used for most pointer conversions; the remaining sites
> were converted by hand.
> 
> Link: https://lore.kernel.org/all/20260903103002.1091859-1-usama.anjum@arm.com/
> Signed-off-by: Muhammad Usama Anjum <usama.anjum@arm.com>

I've been through this as best I can and provided some minor comments. This all
looks ok over all. But given the number of small changes, it would probably be
wise to go big on testing; what level of testing has been performed? I'd suggest
mm selftests (with all the magic to make all the tests actually run) at minimum
and all the fastpath benchmarks as a stress test.

I think it's quite ugly (and adds a bit to the cognitive load) to have this
intermediate state where only ptes are converted. But I understand the need to
do this incrementally. Hopefully you can follow up with the other levels soon :)

Thanks,
Ryan


> ---
> Muhammad Usama Anjum (6):
>       arm64: use hw_pte_t for HW PTE pointers
>       arm64: use hw_pte_val for HW PTE atomics
>       arm64: convert between HW PTEs and SW PTE values
>       arm64: use hw_pte_t for fixmap HW PTEs
>       arm64: use HW PTE accessors in early map_range()
>       arm64: enable a distinct type for HW PTEs
> 
>  arch/arm64/Kconfig                |   1 +
>  arch/arm64/include/asm/hugetlb.h  |  19 ++---
>  arch/arm64/include/asm/pgalloc.h  |   2 +-
>  arch/arm64/include/asm/pgtable.h  | 157 ++++++++++++++++++++------------------
>  arch/arm64/include/asm/vmalloc.h  |   2 +-
>  arch/arm64/kernel/efi.c           |   3 +-
>  arch/arm64/kernel/pi/map_kernel.c |   4 +-
>  arch/arm64/kernel/pi/map_range.c  |  20 +++--
>  arch/arm64/kernel/pi/pi.h         |   3 +-
>  arch/arm64/mm/contpte.c           |  49 ++++++------
>  arch/arm64/mm/fault.c             |  11 +--
>  arch/arm64/mm/fixmap.c            |   8 +-
>  arch/arm64/mm/hugetlbpage.c       |  48 ++++++------
>  arch/arm64/mm/kasan_init.c        |   4 +-
>  arch/arm64/mm/mmu.c               |  46 ++++++-----
>  arch/arm64/mm/pageattr.c          |   4 +-
>  arch/arm64/mm/trans_pgd.c         |   4 +-
>  include/linux/pgtable_types.h     |   6 ++
>  18 files changed, 215 insertions(+), 176 deletions(-)
> ---
> base-commit: ead700ca770c82167af32622cf8b68c9f87c3c7c
> change-id: 20260911-pte0_arm-f1b7df7c0b51
> prerequisite-message-id: 20260903103002.1091859-1-usama.anjum@arm.com
> prerequisite-patch-id: 0114fcc6ab0dbb739b5bb6fc0fe6b1c8f1fa37a1
> prerequisite-patch-id: 09fcf65970074620dd3a9cce6850b901beb01db8
> prerequisite-patch-id: 9b2fdab97c99effabb85526fa7f141c933b3aa23
> prerequisite-patch-id: 1aa309a26d98a1e93a54742705a03567ee93be71
> prerequisite-patch-id: ebe32f52c95ad0542982f0b37798d209595e25e1
> prerequisite-patch-id: a60d249f52d092524176851b2570d7245bb24434
> prerequisite-patch-id: 81ebd1378e25d40a1771b53973abcc4defa87535
> prerequisite-patch-id: d982f2b00c5eddb2459f69008a73e4f4ae4d8299
> 
> Best regards,
> --  
> Usama
>