THREAD_ORDER should be used on 32bit too.
32bit also has the equivalent of irq stacks (quite similar) and exception stacks (somewhat different). Currently they use
other defines, but they could use the same. Also i386 has varying
irqstack orders disabling them with 8k stacks, but that is something
that would be best dropped and irqstacks always used imho.
[...]
It might be, but it's not a 64bit specific concept.
Yes they do, but hardcoding that doesn't make sense because it varies.
We already got CPUs with 36, 38, 40 and 48 bits phys size.
The only size that could be hard coded would be 52 bit (theoretical max), but that also doesn't make sense if all we want to do is to mask off NX.