summaryrefslogtreecommitdiff
path: root/include/uapi/linux/userfaultfd.h
diff options
context:
space:
mode:
authorAndrea Arcangeli <aarcange@redhat.com>2017-02-23 02:43:19 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2017-02-23 03:41:28 +0300
commit163e11bc4f6ebbfcfdf751c108bd212a26e492ee (patch)
tree0379f4659bcf90a473624290bae01eac46b5ddc2 /include/uapi/linux/userfaultfd.h
parent21205bf8f77b23484966cb057ceaec860cc400b3 (diff)
downloadlinux-163e11bc4f6ebbfcfdf751c108bd212a26e492ee.tar.xz
userfaultfd: hugetlbfs: UFFD_FEATURE_MISSING_HUGETLBFS
Userland developers asked to be notified immediately by the UFFDIO_API ioctl if hugetlbfs missing mode is supported by userfaultfd in the running kernel. This avoids the need to run UFFDIO_REGISTER on a hugetlbfs virtual memory range to find out. Link: http://lkml.kernel.org/r/20161216144821.5183-27-aarcange@redhat.com Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Cc: Michael Rapoport <RAPOPORT@il.ibm.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Pavel Emelyanov <xemul@parallels.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/uapi/linux/userfaultfd.h')
-rw-r--r--include/uapi/linux/userfaultfd.h28
1 files changed, 25 insertions, 3 deletions
diff --git a/include/uapi/linux/userfaultfd.h b/include/uapi/linux/userfaultfd.h
index a3828a9bc16e..7293321abdfb 100644
--- a/include/uapi/linux/userfaultfd.h
+++ b/include/uapi/linux/userfaultfd.h
@@ -18,9 +18,10 @@
* means the userland is reading).
*/
#define UFFD_API ((__u64)0xAA)
-#define UFFD_API_FEATURES (UFFD_FEATURE_EVENT_FORK | \
- UFFD_FEATURE_EVENT_REMAP | \
- UFFD_FEATURE_EVENT_MADVDONTNEED)
+#define UFFD_API_FEATURES (UFFD_FEATURE_EVENT_FORK | \
+ UFFD_FEATURE_EVENT_REMAP | \
+ UFFD_FEATURE_EVENT_MADVDONTNEED | \
+ UFFD_FEATURE_MISSING_HUGETLBFS)
#define UFFD_API_IOCTLS \
((__u64)1 << _UFFDIO_REGISTER | \
(__u64)1 << _UFFDIO_UNREGISTER | \
@@ -125,11 +126,32 @@ struct uffdio_api {
* Note: UFFD_EVENT_PAGEFAULT and UFFD_PAGEFAULT_FLAG_WRITE
* are to be considered implicitly always enabled in all kernels as
* long as the uffdio_api.api requested matches UFFD_API.
+ *
+ * UFFD_FEATURE_MISSING_HUGETLBFS means an UFFDIO_REGISTER
+ * with UFFDIO_REGISTER_MODE_MISSING mode will succeed on
+ * hugetlbfs virtual memory ranges. Adding or not adding
+ * UFFD_FEATURE_MISSING_HUGETLBFS to uffdio_api.features has
+ * no real functional effect after UFFDIO_API returns, but
+ * it's only useful for an initial feature set probe at
+ * UFFDIO_API time. There are two ways to use it:
+ *
+ * 1) by adding UFFD_FEATURE_MISSING_HUGETLBFS to the
+ * uffdio_api.features before calling UFFDIO_API, an error
+ * will be returned by UFFDIO_API on a kernel without
+ * hugetlbfs missing support
+ *
+ * 2) the UFFD_FEATURE_MISSING_HUGETLBFS can not be added in
+ * uffdio_api.features and instead it will be set by the
+ * kernel in the uffdio_api.features if the kernel supports
+ * it, so userland can later check if the feature flag is
+ * present in uffdio_api.features after UFFDIO_API
+ * succeeded.
*/
#define UFFD_FEATURE_PAGEFAULT_FLAG_WP (1<<0)
#define UFFD_FEATURE_EVENT_FORK (1<<1)
#define UFFD_FEATURE_EVENT_REMAP (1<<2)
#define UFFD_FEATURE_EVENT_MADVDONTNEED (1<<3)
+#define UFFD_FEATURE_MISSING_HUGETLBFS (1<<4)
__u64 features;
__u64 ioctls;