linux-kernel - [RFC PATCH 0/8] Reimplement huge pages without hugepd on powerpc 8xx

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Date: Mon, 25 Mar 2024 15:55:53 +0100
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Andrew Morton <akpm@...ux-foundation.org>,
	Jason Gunthorpe <jgg@...dia.com>,
	Peter Xu <peterx@...hat.com>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	linuxppc-dev@...ts.ozlabs.org
Subject: [RFC PATCH 0/8] Reimplement huge pages without hugepd on powerpc 8xx

This series reimplements hugepages with hugepd on powerpc 8xx.

Unlike most architectures, powerpc 8xx HW requires a two-level
pagetable topology for all page sizes. So a leaf PMD-contig approach
is not feasible as such.

Possible sizes are 4k, 16k, 512k and 8M.

First level (PGD/PMD) covers 4M per entry. For 8M pages, two PMD entries
must point to a single entry level-2 page table. Until now that was
done using hugepd. This series changes it to use standard page tables
where the entry is replicated 1024 times on each of the two pagetables
refered by the two associated PMD entries for that 8M page.

At the moment it has to look into each helper to know if the
hugepage ptep is a PTE or a PMD in order to know it is a 8M page or
a lower size. I hope this can me handled by core-mm in the future.

There are probably several ways to implement stuff, so feedback is
very welcome.

Christophe Leroy (8):
  mm: Provide pagesize to pmd_populate()
  mm: Provide page size to pte_alloc_huge()
  mm: Provide pmd to pte_leaf_size()
  mm: Provide mm_struct and address to huge_ptep_get()
  powerpc/mm: Allow hugepages without hugepd
  powerpc/8xx: Fix size given to set_huge_pte_at()
  powerpc/8xx: Remove support for 8M pages
  powerpc/8xx: Add back support for 8M pages using contiguous PTE
    entries

 arch/arm64/include/asm/hugetlb.h              |  2 +-
 arch/arm64/include/asm/pgtable.h              |  2 +-
 arch/arm64/mm/hugetlbpage.c                   |  2 +-
 arch/parisc/mm/hugetlbpage.c                  |  2 +-
 arch/powerpc/Kconfig                          |  1 -
 arch/powerpc/include/asm/hugetlb.h            | 13 +++-
 .../include/asm/nohash/32/hugetlb-8xx.h       | 54 ++++++++---------
 arch/powerpc/include/asm/nohash/32/pgalloc.h  |  2 +
 arch/powerpc/include/asm/nohash/32/pte-8xx.h  | 59 +++++++++++++------
 arch/powerpc/include/asm/nohash/pgtable.h     | 12 ++--
 arch/powerpc/include/asm/page.h               |  5 --
 arch/powerpc/include/asm/pgtable.h            |  1 +
 arch/powerpc/kernel/head_8xx.S                | 10 +---
 arch/powerpc/mm/hugetlbpage.c                 | 23 +++++++-
 arch/powerpc/mm/nohash/8xx.c                  | 46 +++++++--------
 arch/powerpc/mm/pgtable.c                     | 26 +++++---
 arch/powerpc/mm/pgtable_32.c                  |  2 +-
 arch/powerpc/platforms/Kconfig.cputype        |  2 +
 arch/riscv/include/asm/pgtable.h              |  2 +-
 arch/riscv/mm/hugetlbpage.c                   |  2 +-
 arch/sh/mm/hugetlbpage.c                      |  2 +-
 arch/sparc/include/asm/pgtable_64.h           |  2 +-
 arch/sparc/mm/hugetlbpage.c                   |  4 +-
 fs/hugetlbfs/inode.c                          |  2 +-
 fs/proc/task_mmu.c                            |  8 +--
 fs/userfaultfd.c                              |  2 +-
 include/asm-generic/hugetlb.h                 |  2 +-
 include/linux/hugetlb.h                       |  4 +-
 include/linux/mm.h                            | 12 ++--
 include/linux/pgtable.h                       |  2 +-
 include/linux/swapops.h                       |  2 +-
 kernel/events/core.c                          |  2 +-
 mm/damon/vaddr.c                              |  6 +-
 mm/filemap.c                                  |  2 +-
 mm/gup.c                                      |  2 +-
 mm/hmm.c                                      |  2 +-
 mm/hugetlb.c                                  | 46 +++++++--------
 mm/internal.h                                 |  2 +-
 mm/memory-failure.c                           |  2 +-
 mm/memory.c                                   | 19 +++---
 mm/mempolicy.c                                |  2 +-
 mm/migrate.c                                  |  4 +-
 mm/mincore.c                                  |  2 +-
 mm/pgalloc-track.h                            |  2 +-
 mm/userfaultfd.c                              |  6 +-
 45 files changed, 229 insertions(+), 180 deletions(-)

-- 
2.43.0