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Subject[PATCH v10 2/6] userfaultfd: update documentation to describe UFFD_FEATURE_WP_ASYNC
Date
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@collabora.com>
---
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
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