Re: [PATCH v4 09/10] userfaultfd: update documentation to describe minor fault handling
From: Randy Dunlap <hidden>
Date: 2021-02-04 19:59:45
Also in:
linux-mm, lkml
Hi Axel- one typo found: On 2/4/21 10:34 AM, Axel Rasmussen wrote:
Reword / reorganize things a little bit into "lists", so new features / modes / ioctls can sort of just be appended.
Good plan.
quoted hunk ↗ jump to hunk
Signed-off-by: Axel Rasmussen <axelrasmussen@google.com> --- Documentation/admin-guide/mm/userfaultfd.rst | 107 ++++++++++++------- 1 file changed, 66 insertions(+), 41 deletions(-)diff --git a/Documentation/admin-guide/mm/userfaultfd.rst b/Documentation/admin-guide/mm/userfaultfd.rst index 65eefa66c0ba..cfd3daf59d0e 100644 --- a/Documentation/admin-guide/mm/userfaultfd.rst +++ b/Documentation/admin-guide/mm/userfaultfd.rst
[snip]
- -Once the ``userfaultfd`` has been enabled the ``UFFDIO_REGISTER`` ioctl should -be invoked (if present in the returned ``uffdio_api.ioctls`` bitmask) to -register a memory range in the ``userfaultfd`` by setting the +events, except page fault notifications, may be generated: + +- The ``UFFD_FEATURE_EVENT_*`` flags indicate that various other events + other than page faults are supported. These events are described in more + detail below in the `Non-cooperative userfaultfd`_ section. + +- ``UFFD_FEATURE_MISSING_HUGETLBFS`` and ``UFFD_FEATURE_MISSING_SHMEM`` + indicate that the kernel supports ``UFFDIO_REGISTER_MODE_MISSING`` + registrations for hugetlbfs and shared memory (covering all shmem APIs, + i.e. tmpfs, ``IPCSHM``, ``/dev/zero``, ``MAP_SHARED``, ``memfd_create``, + etc) virtual memory areas, respectively. + +- ``UFFD_FEATURE_MINOR_HUGETLBFS`` indicates that the kernel supports + ``UFFDIO_REGISTER_MODE_MINOR`` registration for hugetlbfs virtual memory + areas. + +The userland application should set the feature flags it intends to use
(ah, userspace has moved to userland temporarily. :)
+when envoking the ``UFFDIO_API`` ioctl, to request that those features be
invoking
+enabled if supported.
thanks. -- ~Randy