Creating a new Nested Virtualization meta bug to track current Nested Virtualization issues. I can't edit the old meta bug (bug 53601) due to permission issues, Nadav suggested to close it.
Added "Depends on" bugs. Note that some of them might have been already fixed. I will go through them and either remove them here or add a comment, since only the reporter seem to have permissions to close bugs.
*** Bug 53601 has been marked as a duplicate of this bug. ***