These changes are based on Jason's latest hmm branch. Patch 1 was previously posted here [1] but was dropped from the orginal series. Hopefully, the tests will reduce concerns about edge conditions. I'm sure more tests could be usefully added but I thought this was a good starting point.
[1] https://lore.kernel.org/linux-mm/20190726005650.2566-6-rcampbell@nvidia.com/
Ralph Campbell (4): mm/hmm: make full use of walk_page_range() mm/hmm: allow snapshot of the special zero page mm/hmm: allow hmm_range_fault() of mmap(PROT_NONE) mm/hmm/test: add self tests for HMM
MAINTAINERS | 3 + drivers/char/Kconfig | 11 + drivers/char/Makefile | 1 + drivers/char/hmm_dmirror.c | 1504 ++++++++++++++++++++++++ include/Kbuild | 1 + include/uapi/linux/hmm_dmirror.h | 74 ++ mm/hmm.c | 117 +- tools/testing/selftests/vm/.gitignore | 1 + tools/testing/selftests/vm/Makefile | 3 + tools/testing/selftests/vm/config | 3 + tools/testing/selftests/vm/hmm-tests.c | 1304 ++++++++++++++++++++ tools/testing/selftests/vm/run_vmtests | 16 + tools/testing/selftests/vm/test_hmm.sh | 105 ++ 13 files changed, 3079 insertions(+), 64 deletions(-) create mode 100644 drivers/char/hmm_dmirror.c create mode 100644 include/uapi/linux/hmm_dmirror.h create mode 100644 tools/testing/selftests/vm/hmm-tests.c create mode 100755 tools/testing/selftests/vm/test_hmm.sh