[PATCH V3 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(9) 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[1] and simple_loop [2] dump and restores work fine;
- zdtm test suite can run under host mode.

V3:
- Fixed the issue reported by kernel test irobot <lkp at intel.com>.

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.

[1] https://www.criu.org/Incremental_dumps
[2] https://asciinema.org/a/232445

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