diff options
| author | Andrea Arcangeli | 2017-02-22 15:43:19 -0800 |
|---|---|---|
| committer | Linus Torvalds | 2017-02-22 16:41:28 -0800 |
| commit | 163e11bc4f6ebbfcfdf751c108bd212a26e492ee (patch) | |
| tree | 0379f4659bcf90a473624290bae01eac46b5ddc2 | |
| parent | 21205bf8f77b23484966cb057ceaec860cc400b3 (diff) | |
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>
| -rw-r--r-- | include/uapi/linux/userfaultfd.h | 28 |
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; |