riscv: mm: Add soft-dirty and uffd-wp support

This patchset adds support for Svrsw60t59b [1] extension which is ratified now,
also add soft dirty and userfaultfd write protect tracking for RISC-V.

The patches 1 and 2 add macros to allow architectures to define their own checks
if the soft-dirty / uffd_wp PTE bits are available, in other words for RISC-V,
the Svrsw60t59b extension is supported on which device the kernel is running.
Also patch1-2 are removing "ifdef CONFIG_MEM_SOFT_DIRTY"
"ifdef CONFIG_HAVE_ARCH_USERFAULTFD_WP" and
"ifdef CONFIG_PTE_MARKER_UFFD_WP" in favor of checks which if not overridden by
the architecture, no change in behavior is expected.

This patchset has been tested with kselftest mm suite in which soft-dirty, 
madv_populate, test_unmerge_uffd_wp, and uffd-unit-tests run and pass,
and no regressions are observed in any of the other tests.

This patchset applies on top of the lastest mm-new branch.

[1] https://github.com/riscv-non-isa/riscv-iommu/pull/543

V14:
- Fix indent inssues in userfaultfd_k.h;
- Some descriptions and comments minor changes.

V13: https://lore.kernel.org/all/20250917033703.1695933-1-zhan...
- Rebase on mm-new branch;
- Fixed build errors;
- Add more exactly descriptions in commit message in patch 1-2;
- Replace '__always_inline' with 'inline' for uffd_supports_wp_marker();
- Add Svrsw60t59b description to the extensions dt-binding in patch 6.

V12: https://lore.kernel.org/all/20250915101343.1449546-1-zhan...
- Rename the macro API to pgtable_supports_soft_dirty/uffd_wp();
- Add changes for setting VM_SOFTDIRTY flags conditionally;
- Drop changes to show_smap_vma_flags();
- Drop CONFIG_MEM_SOFT_DIRTY compile condition of clear_soft_dirty() and clear_soft_dirty_pmd();
- Fix typos;
- Add uffd_supports_wp_marker() and drop some ifdef CONFIG_PTE_MARKER_UFFD_WP.

V11: https://lore.kernel.org/all/20250911095602.1130290-1-zhan...
- Rename the macro API to pgtable_*_supported() since we also have PMD support;
- Change the default implementations of two macros, make CONFIG_MEM_SOFT_DIRTY or
  CONFIG_HAVE_ARCH_USERFAULTFD_WP part of the macros;
- Correct the order of insertion of RISCV_ISA_EXT_SVRSW60T59B;
- Rephrase some comments.

V10: https://lore.kernel.org/all/20250909095611.803898-1-zhang...
- Fixed the issue reported by kernel test irobot <lkp@intel.com>.

V9: https://lore.kernel.org/all/20250905103651.489197-1-zhang...
- Add pte_soft_dirty/uffd_wp_available() API to allow dynamically checking
  if the PTE bit is available for the platform on which the kernel is running.

V8: https://lore.kernel.org/all/20250619065232.1786470-1-zhan...)
- Rebase on v6.16-rc1;
- Add dependencies to MMU && 64BIT for RISCV_ISA_SVRSW60T59B;
- Use 'Svrsw60t59b' instead of 'SVRSW60T59B' in Kconfig help paragraph;
- Add Alex's Reviewed-by tag in patch 1.

V7: https://lore.kernel.org/all/20250409095320.224100-1-zhang...
- Add Svrsw60t59b [1] extension support;
- Have soft-dirty and uffd-wp depending on the Svrsw60t59b extension to
  avoid crashes for the hardware which don't have this extension.

V6: https://lore.kernel.org/all/20250408084301.68186-1-zhangc...
- Changes to use bits 59-60 which are supported by extension Svrsw60t59b
  for soft dirty and userfaultfd write protect tracking.

V5: https://lore.kernel.org/all/20241113095833.1805746-1-zhan...
- Fixed typos and corrected some words in Kconfig and commit message;
- Removed pte_wrprotect() from pte_swp_mkuffd_wp(), this is a copy-paste
  error;
- Added Alex's Reviewed-by tag in patch 2.

V4: https://lore.kernel.org/all/20240830011101.3189522-1-zhan...
- Added bit(4) descriptions into "Format of swap PTE".

V3: https://lore.kernel.org/all/20240805095243.44809-1-zhangc...
- Fixed the issue reported by kernel test irobot <lkp@intel.com>.

V2: https://lore.kernel.org/all/20240731040444.3384790-1-zhan...
- Add uffd-wp supported;
- Make soft-dirty uffd-wp and devmap mutually exclusive which all use
  the same PTE bit;
- Add test results of CRIU in the cover-letter.

Chunyan Zhang (6):
  mm: softdirty: Add pgtable_supports_soft_dirty()
  mm: userfaultfd: Add pgtable_supports_uffd_wp()
  riscv: Add RISC-V Svrsw60t59b extension support
  riscv: mm: Add soft-dirty page tracking support
  riscv: mm: Add userfaultfd write-protect support
  dt-bindings: riscv: Add Svrsw60t59b extension description

 .../devicetree/bindings/riscv/extensions.yaml |   6 +
 arch/riscv/Kconfig                            |  16 ++
 arch/riscv/include/asm/hwcap.h                |   1 +
 arch/riscv/include/asm/pgtable-bits.h         |  37 +++++
 arch/riscv/include/asm/pgtable.h              | 143 +++++++++++++++++-
 arch/riscv/kernel/cpufeature.c                |   1 +
 fs/proc/task_mmu.c                            |  15 +-
 fs/userfaultfd.c                              |  22 +--
 include/asm-generic/pgtable_uffd.h            |  17 +++
 include/linux/mm.h                            |   3 +
 include/linux/mm_inline.h                     |   8 +-
 include/linux/pgtable.h                       |  12 ++
 include/linux/userfaultfd_k.h                 | 114 ++++++++------
 mm/debug_vm_pgtable.c                         |  10 +-
 mm/huge_memory.c                              |  13 +-
 mm/internal.h                                 |   2 +-
 mm/memory.c                                   |   6 +-
 mm/mmap.c                                     |   6 +-
 mm/mremap.c                                   |  13 +-
 mm/userfaultfd.c                              |  10 +-
 mm/vma.c                                      |   6 +-
 mm/vma_exec.c                                 |   5 +-
 22 files changed, 361 insertions(+), 105 deletions(-)

-- 
2.34.1