[PATCH V2 0/3] riscv: mm: Add soft-dirty and uffd-wp support

[Chunyan Zhang]

This patchset adds soft dirty and userfaultfd write protect tracking support
for RISC-V.

As described in the patches, we are trying to utilize only one free PTE bit to
support three kernel features (devmap, soft-dirty,uffd-wp). Users cannot have
them supported at the same time (have to select one when building the kernel).

This patchset has been tested with:
1) The 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.

2) CRIU:
- 'criu check --feature mem_dirty_track' returns supported
- incremental_dumps works fine
- zdtm test suite can run under host mode

V1 -> V2:
- 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 (3):
  riscv: mm: Prepare for reuse PTE RSW bit(9)
  riscv: mm: Add soft-dirty page tracking support
  riscv: mm: Add uffd write-protect support

 arch/riscv/Kconfig                    |  34 ++++++-
 arch/riscv/include/asm/pgtable-64.h   |   2 +-
 arch/riscv/include/asm/pgtable-bits.h |  31 ++++++
 arch/riscv/include/asm/pgtable.h      | 132 +++++++++++++++++++++++++-
 4 files changed, 196 insertions(+), 3 deletions(-)

-- 
2.34.1