Explain the difference created by UFFD_FEATURE_WP_ASYNC to the write protection (UFFDIO_WRITEPROTECT_MODE_WP) mode. Signed-off-by: Muhammad Usama Anjum <usama.anjum@xxxxxxxxxxxxx> --- Documentation/admin-guide/mm/userfaultfd.rst | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/Documentation/admin-guide/mm/userfaultfd.rst b/Documentation/admin-guide/mm/userfaultfd.rst index 83f31919ebb3..4747e7bd5b26 100644 --- a/Documentation/admin-guide/mm/userfaultfd.rst +++ b/Documentation/admin-guide/mm/userfaultfd.rst @@ -221,6 +221,13 @@ former will have ``UFFD_PAGEFAULT_FLAG_WP`` set, the latter you still need to supply a page when ``UFFDIO_REGISTER_MODE_MISSING`` was used. +If ``UFFD_FEATURE_WP_ASYNC`` is set while calling ``UFFDIO_API`` ioctl, the +behaviour of ``UFFDIO_WRITEPROTECT_MODE_WP`` changes such that faults for +anon and shmem are resolved automatically by the kernel instead of sending +the message to the userfaultfd. The hugetlb isn't supported. The ``pagemap`` +file can be read to find which pages have ``PM_UFFD_WP`` flag set which +means they are write-protected. + QEMU/KVM ======== -- 2.30.2
