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When this capability is enabled, QEMU will use the return path even for precopy migration. This is helpful at least in one case when destination failed to load the image while source quited without confirmation. With return path, source will wait for the last response from destination, and if destination fails, it'll fail the migration on source, then the guest can be run again on the source (rather than assuming to be good, then the guest will be lost after source quits). It needs to be enabled explicitly on source, otherwise disabled. Signed-off-by: Peter Xu <peterx@redhat.com> Message-Id: <1498472935-14461-1-git-send-email-peterx@redhat.com> Reviewed-by: Juan Quintela <quintela@redhat.com> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com> Signed-off-by: Juan Quintela <quintela@redhat.com>