On Wed, Feb 26, 2020 at 04:53:04PM +0100, David Hildenbrand wrote: > When we partially change mappings (esp., mmap over parts of an existing > mmap like qemu_ram_remap() does) where we have a userfaultfd handler > registered, the handler will implicitly be unregistered from the parts that > changed. > > Trying to place pages onto mappings where there is no longer a handler > registered will fail. Let's make sure that any waiter is woken up - we > have to do that manually. > > Let's also document how UFFDIO_UNREGISTER will handle this scenario. > > This is mainly a preparation for RAM blocks with resizable allcoations, > where the mapping of the invalid RAM range will change. The source will > keep sending pages that are outside of the new (shrunk) RAM size. We have > to treat these pages like they would have been migrated, but can > essentially simply drop the content (ignore the placement error). > > Keep printing a warning when we hit EINVAL, to avoid hiding other > (programming) issues. ENOENT is unique. > > Cc: "Dr. David Alan Gilbert" <[email protected]> > Cc: Juan Quintela <[email protected]> > Cc: Peter Xu <[email protected]> > Cc: Andrea Arcangeli <[email protected]> > Signed-off-by: David Hildenbrand <[email protected]>
Reviewed-by: Peter Xu <[email protected]> -- Peter Xu
