Not only is copying it over itself not the only solution (all you need to do is issue the right sequence of cache flushes over the affected area, so first CPU c

Not only is copying it over itself not the only solution (all you need to do is issue the right sequence of cache flushes over the affected area, so first CPU cache flush instructions, and then maybe an additional set of MMIO based cache flushes depending on how your L2 and/or L3 work), but copying over itself isn't even enough to be correct. They lucked out that it seems to work, but it's kind of by chance. That cache is more than in the right to still not flush some lines even with this big copy.