On 26.02.20 17:06, Peter Xu wrote: > 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" <dgilb...@redhat.com> >> Cc: Juan Quintela <quint...@redhat.com> >> Cc: Peter Xu <pet...@redhat.com> >> Cc: Andrea Arcangeli <aarca...@redhat.com> >> Signed-off-by: David Hildenbrand <da...@redhat.com> > > Reviewed-by: Peter Xu <pet...@redhat.com> >
Thanks a lot! BTW, while I am playing with userfaultfd, I already have patches to factor out all uffd handling from postcopy code into utils/uffd.c My list of patches does not seem to get any smaller :( -- Thanks, David / dhildenb
