The features handshake is not quite convenient. Elaborate about it in the BUGS section.
Signed-off-by: Mike Rapoport <r...@linux.vnet.ibm.com> --- man2/ioctl_userfaultfd.2 | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/man2/ioctl_userfaultfd.2 b/man2/ioctl_userfaultfd.2 index e12b9de..50316de 100644 --- a/man2/ioctl_userfaultfd.2 +++ b/man2/ioctl_userfaultfd.2 @@ -650,6 +650,15 @@ operations are Linux-specific. .SH EXAMPLE See .BR userfaultfd (2). +.SH BUGS +In order to detect available userfault features and +enable certain subset of those features +the usefault file descriptor must be closed after the first +.BR UFFDIO_API +operation that queries features availability and re-opened before +the second +.BR UFFDIO_API +call that actually enables the desired features. .SH SEE ALSO .BR ioctl (2), .BR mmap (2), -- 1.9.1
