> This strategy seems to work quite well, and I think it would be nice
> if in the future amd64 would use the same model.

With the legacy bootloader, I think it is difficult to allocate memory
correctly, and then furthermore --  place code high if that is the
decided location.

Anyways, the goal is to avoid the PA overlapping some weird object
in the address space on weird machines.  There's no security benefit
from being at such a PA.