linux-kernel - Re: [PATCH v2 0/9] Merge arm64/riscv hugetlbfs contpte support

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Date: Wed, 8 May 2024 13:32:00 +0200
From: Alexandre Ghiti <alex@...ti.fr>
To: Alexandre Ghiti <alexghiti@...osinc.com>,
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
 Ryan Roberts <ryan.roberts@....com>, Mark Rutland <mark.rutland@....com>,
 Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt
 <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
 Andrew Morton <akpm@...ux-foundation.org>,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 linux-riscv@...ts.infradead.org, linux-mm@...ck.org
Subject: Re: [PATCH v2 0/9] Merge arm64/riscv hugetlbfs contpte support

I should not have unplugged this outlet...Sorry, ignore this series, I'm 
sending a RESEND right away.

On 08/05/2024 13:18, Alexandre Ghiti wrote:
> This patchset intends to merge the contiguous ptes hugetlbfs implementation
> of arm64 and riscv.
>
> Both arm64 and riscv support the use of contiguous ptes to map pages that
> are larger than the default page table size, respectively called contpte
> and svnapot.
>
> The riscv implementation differs from the arm64's in that the LSBs of the
> pfn of a svnapot pte are used to store the size of the mapping, allowing
> for future sizes to be added (for now only 64KB is supported). That's an
> issue for the core mm code which expects to find the *real* pfn a pte points
> to. Patch 1 fixes that by always returning svnapot ptes with the real pfn
> and restores the size of the mapping when it is written to a page table.
>
> The following patches are just merges of the 2 different implementations
> that currently exist in arm64 and riscv which are very similar. It paves
> the way to the reuse of the recent contpte THP work by Ryan [1] to avoid
> reimplementing the same in riscv.
>
> This patchset was tested by running the libhugetlbfs testsuite with 64KB
> and 2MB pages on both architectures (on a 4KB base page size arm64 kernel).
>
> [1] https://lore.kernel.org/linux-arm-kernel/20240215103205.2607016-1-ryan.roberts@arm.com/
>
> Changes in v2:
>    - Rebase on top of 6.9-rc3
>
> Alexandre Ghiti (9):
>    riscv: Restore the pfn in a NAPOT pte when manipulated by core mm code
>    riscv: Safely remove huge_pte_offset() when manipulating NAPOT ptes
>    mm: Use common huge_ptep_get() function for riscv/arm64
>    mm: Use common set_huge_pte_at() function for riscv/arm64
>    mm: Use common huge_pte_clear() function for riscv/arm64
>    mm: Use common huge_ptep_get_and_clear() function for riscv/arm64
>    mm: Use common huge_ptep_set_access_flags() function for riscv/arm64
>    mm: Use common huge_ptep_set_wrprotect() function for riscv/arm64
>    mm: Use common huge_ptep_clear_flush() function for riscv/arm64
>
>   arch/arm64/Kconfig                  |   1 +
>   arch/arm64/include/asm/pgtable.h    |  56 +++++-
>   arch/arm64/mm/hugetlbpage.c         | 291 +---------------------------
>   arch/riscv/Kconfig                  |   1 +
>   arch/riscv/include/asm/hugetlb.h    |   2 +-
>   arch/riscv/include/asm/pgtable-64.h |  11 ++
>   arch/riscv/include/asm/pgtable.h    | 153 +++++++++++++--
>   arch/riscv/mm/hugetlbpage.c         | 227 ----------------------
>   arch/riscv/mm/pgtable.c             |   6 +-
>   mm/Kconfig                          |   3 +
>   mm/Makefile                         |   1 +
>   mm/contpte.c                        | 272 ++++++++++++++++++++++++++
>   12 files changed, 480 insertions(+), 544 deletions(-)
>   create mode 100644 mm/contpte.c
>