This is used by "-realtime mlock=on".

Signed-off-by: Eduardo Otubo <eduardo.otubo@profitbricks.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Amit Shah <amit.shah@redhat.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Tested-by: Eduardo Habkost <ehabkost@redhat.com>
Acked-by: Eduardo Otubo <eduardo.otubo@profitbricks.com>