Instead of checking for availability of userfaultfd late during the restore
process, make the detection of supported userfaultfd functionality part of
kerndat. As a bonus, I've extended criu check with ability to verify
presence of userfaultfd.
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>