[PATCH v4 00/45] Use hugepages to map kernel mem on 8xx

Christophe Leroy christophe.leroy at csgroup.eu
Tue May 19 15:48:42 AEST 2020

The main purpose of this big series is to:
- reorganise huge page handling to avoid using mm_slices.
- use huge pages to map kernel memory on the 8xx.

The 8xx supports 4 page sizes: 4k, 16k, 512k and 8M.
It uses 2 Level page tables, PGD having 1024 entries, each entry
covering 4M address space. Then each page table has 1024 entries.

At the time being, page sizes are managed in PGD entries, implying
the use of mm_slices as it can't mix several pages of the same size
in one page table.

The first purpose of this series is to reorganise things so that
standard page tables can also handle 512k pages. This is done by
adding a new _PAGE_HUGE flag which will be copied into the Level 1
entry in the TLB miss handler. That done, we have 2 types of pages:
- PGD entries to regular page tables handling 4k/16k and 512k pages
- PGD entries to hugepd tables handling 8M pages.

There is no need to mix 8M pages with other sizes, because a 8M page
will use more than what a single PGD covers.

Then comes the second purpose of this series. At the time being, the
8xx has implemented special handling in the TLB miss handlers in order
to transparently map kernel linear address space and the IMMR using
huge pages by building the TLB entries in assembly at the time of the

As mm_slices is only for user space pages, and also because it would
anyway not be convenient to slice kernel address space, it was not
possible to use huge pages for kernel address space. But after step
one of the series, it is now more flexible to use huge pages.

This series drop all assembly 'just in time' handling of huge pages
and use huge pages in page tables instead.

Once the above is done, then comes icing on the cake:
- Use huge pages for KASAN shadow mapping
- Allow pinned TLBs with strict kernel rwx
- Allow pinned TLBs with debug pagealloc

Then, last but not least, those modifications for the 8xx allows the
following improvement on book3s/32:
- Mapping KASAN shadow with BATs
- Allowing BATs with debug pagealloc

All this allows to considerably simplify TLB miss handlers and associated
initialisation. The overhead of reading page tables is negligible
compared to the reduction of the miss handlers.

While we were at touching pte_update(), some cleanup was done
there too.

Tested widely on 8xx and 832x. Boot tested on QEMU MAC99.

Changes in v4:
- Rebased on top of powerpc/next following the merge of prefix instructions series.

Changes in v3:
- Fixed the handling of leaf pages page size which didn't build on PPC64 and was invisibily bogus on PPC32 (patch 12)

Changes in v2:
- Selecting HUGETLBFS instead of HUGETLB_PAGE which leads to link failure.
- Rebase on latest powerpc/merge branch
- Reworked the way TLB 28 to 31 are pinned because it was not working.

Christophe Leroy (45):
  powerpc/kasan: Fix error detection on memory allocation
  powerpc/kasan: Fix issues by lowering KASAN_SHADOW_END
  powerpc/kasan: Fix shadow pages allocation failure
  powerpc/kasan: Remove unnecessary page table locking
  powerpc/kasan: Refactor update of early shadow mappings
  powerpc/kasan: Declare kasan_init_region() weak
  powerpc/ptdump: Limit size of flags text to 1/2 chars on PPC32
  powerpc/ptdump: Reorder flags
  powerpc/ptdump: Add _PAGE_COHERENT flag
  powerpc/ptdump: Display size of BATs
  powerpc/ptdump: Standardise display of BAT flags
  powerpc/ptdump: Properly handle non standard page size
  powerpc/ptdump: Handle hugepd at PGD level
  powerpc/32s: Don't warn when mapping RO data ROX.
  powerpc/mm: Allocate static page tables for fixmap
  powerpc/mm: Fix conditions to perform MMU specific management by
    blocks on PPC32.
  powerpc/mm: PTE_ATOMIC_UPDATES is only for 40x
  powerpc/mm: Refactor pte_update() on nohash/32
  powerpc/mm: Refactor pte_update() on book3s/32
  powerpc/mm: Standardise __ptep_test_and_clear_young() params between
    PPC32 and PPC64
  powerpc/mm: Standardise pte_update() prototype between PPC32 and PPC64
  powerpc/mm: Create a dedicated pte_update() for 8xx
  powerpc/mm: Reduce hugepd size for 8M hugepages on 8xx
  powerpc/8xx: Drop CONFIG_8xx_COPYBACK option
  powerpc/8xx: Prepare handlers for _PAGE_HUGE for 512k pages.
  powerpc/8xx: Manage 512k huge pages as standard pages.
  powerpc/8xx: Only 8M pages are hugepte pages now
  powerpc/8xx: MM_SLICE is not needed anymore
  powerpc/8xx: Move PPC_PIN_TLB options into 8xx Kconfig
  powerpc/8xx: Add function to set pinned TLBs
  powerpc/8xx: Don't set IMMR map anymore at boot
  powerpc/8xx: Always pin TLBs at startup.
  powerpc/8xx: Drop special handling of Linear and IMMR mappings in I/D
    TLB handlers
  powerpc/8xx: Remove now unused TLB miss functions
  powerpc/8xx: Move DTLB perf handling closer.
  powerpc/mm: Don't be too strict with _etext alignment on PPC32
  powerpc/8xx: Refactor kernel address boundary comparison
  powerpc/8xx: Add a function to early map kernel via huge pages
  powerpc/8xx: Map IMMR with a huge page
  powerpc/8xx: Map linear memory with huge pages
  powerpc/8xx: Allow STRICT_KERNEL_RwX with pinned TLB
  powerpc/8xx: Allow large TLBs with DEBUG_PAGEALLOC
  powerpc/8xx: Implement dedicated kasan_init_region()
  powerpc/32s: Allow mapping with BATs with DEBUG_PAGEALLOC
  powerpc/32s: Implement dedicated kasan_init_region()

 arch/powerpc/Kconfig                          |  62 +--
 arch/powerpc/configs/adder875_defconfig       |   1 -
 arch/powerpc/configs/ep88xc_defconfig         |   1 -
 arch/powerpc/configs/mpc866_ads_defconfig     |   1 -
 arch/powerpc/configs/mpc885_ads_defconfig     |   1 -
 arch/powerpc/configs/tqm8xx_defconfig         |   1 -
 arch/powerpc/include/asm/book3s/32/pgtable.h  |  78 ++--
 arch/powerpc/include/asm/fixmap.h             |   4 +
 arch/powerpc/include/asm/hugetlb.h            |   4 -
 arch/powerpc/include/asm/kasan.h              |  10 +-
 .../include/asm/nohash/32/hugetlb-8xx.h       |  32 +-
 arch/powerpc/include/asm/nohash/32/mmu-8xx.h  |  74 +---
 arch/powerpc/include/asm/nohash/32/pgtable.h  | 104 +++--
 arch/powerpc/include/asm/nohash/32/pte-8xx.h  |   4 +-
 arch/powerpc/include/asm/nohash/32/slice.h    |  20 -
 arch/powerpc/include/asm/nohash/64/pgtable.h  |  28 +-
 arch/powerpc/include/asm/nohash/pgtable.h     |   2 +-
 arch/powerpc/include/asm/pgtable.h            |   2 +
 arch/powerpc/include/asm/slice.h              |   2 -
 arch/powerpc/kernel/head_8xx.S                | 354 ++++++++----------
 arch/powerpc/kernel/setup_32.c                |   2 +-
 arch/powerpc/kernel/vmlinux.lds.S             |   3 +-
 arch/powerpc/mm/book3s32/mmu.c                |  12 +-
 arch/powerpc/mm/hugetlbpage.c                 |  41 +-
 arch/powerpc/mm/init_32.c                     |  12 +-
 arch/powerpc/mm/kasan/8xx.c                   |  74 ++++
 arch/powerpc/mm/kasan/Makefile                |   2 +
 arch/powerpc/mm/kasan/book3s_32.c             |  57 +++
 arch/powerpc/mm/kasan/kasan_init_32.c         |  88 ++---
 arch/powerpc/mm/mmu_decl.h                    |   4 +
 arch/powerpc/mm/nohash/8xx.c                  | 226 ++++++-----
 arch/powerpc/mm/pgtable.c                     |  34 +-
 arch/powerpc/mm/pgtable_32.c                  |  22 +-
 arch/powerpc/mm/ptdump/8xx.c                  |  52 +--
 arch/powerpc/mm/ptdump/bats.c                 |  41 +-
 arch/powerpc/mm/ptdump/ptdump.c               |  71 +++-
 arch/powerpc/mm/ptdump/ptdump.h               |   3 +
 arch/powerpc/mm/ptdump/shared.c               |  58 +--
 arch/powerpc/perf/8xx-pmu.c                   |  10 -
 arch/powerpc/platforms/8xx/Kconfig            |  50 ++-
 arch/powerpc/platforms/Kconfig.cputype        |   2 +-
 arch/powerpc/sysdev/cpm_common.c              |   2 +
 42 files changed, 853 insertions(+), 798 deletions(-)
 delete mode 100644 arch/powerpc/include/asm/nohash/32/slice.h
 create mode 100644 arch/powerpc/mm/kasan/8xx.c
 create mode 100644 arch/powerpc/mm/kasan/book3s_32.c


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