Re: [PATCH v3 13/16] selftests/mm: add userfaultfd RWP tests

[Mike Rapoport <rppt@kernel.org>]

On Fri, May 22, 2026 at 02:38:54PM +0100, Kiryl Shutsemau wrote:
> From: "Kiryl Shutsemau (Meta)" <kas@kernel.org>
> 
> Coverage for UFFDIO_REGISTER_MODE_RWP and UFFDIO_RWPROTECT:
> 
>   rwp-async          async mode — touch pages, verify permissions are
>                      auto-restored without a message
>   rwp-sync           sync mode — access blocks, handler resolves via
>                      UFFDIO_RWPROTECT
>   rwp-pagemap        PAGEMAP_SCAN reports still-cold pages via
>                      inverted PAGE_IS_ACCESSED
>   rwp-mprotect       RWP survives mprotect(PROT_NONE) ->
>                      mprotect(PROT_READ|PROT_WRITE) round-trip
>   rwp-gup            GUP walks through a protnone RWP PTE (pipe
>                      write/read drives the GUP path)
>   rwp-async-toggle   UFFDIO_SET_MODE flips between sync and async
>                      without re-registering
>   rwp-close          closing the uffd restores page permissions
>   rwp-fork           RWP survives fork() with EVENT_FORK; child's
>                      PTEs keep the uffd bit
>   rwp-fork-pin       RWP survives fork() on an RO-longterm-pinned
>                      anon page (forces copy_present_page()); child
>                      read auto-resolves and clears the bit, proving
>                      PAGE_NONE was in place
>   rwp-wp-exclusive   register with MODE_WP|MODE_RWP returns -EINVAL
> 
> All tests run against anon, shmem, shmem-private, hugetlb, and
> hugetlb-private memory, except rwp-fork-pin which is anon-only —
> copy_present_page() is the private-anon pinned-exclusive fork path.
> 
> Signed-off-by: Kiryl Shutsemau <kas@kernel.org>
> Assisted-by: Claude:claude-opus-4-6

Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>

> ---
>  tools/testing/selftests/mm/uffd-unit-tests.c | 766 +++++++++++++++++++
>  1 file changed, 766 insertions(+)

-- 
Sincerely yours,
Mike.