Some evidence about the PowerMac G5 multiprocessor boot hang ups with the modern VM_MAX_KERNEL_ADDRESS value

[Justin Hibbits]

On Fri, 15 Feb 2019 11:51:26 -0800
Mark Millard via freebsd-ppc <freebsd-ppc at freebsd.org> wrote:

> Old: 0xe0000000013ff0??
> New: 0xe000000087fd20??

The addresses are pretty inconsequential, since they're virtual
addresses.  It would be nice to be able to profile how far a CPU gets
in its launch (writing a value to a well-known address,
0xc000000000000010, or such, anywhere in the bottom 256 bytes of space
really).  If you add writes to that address, we can track the progress
at panic time.  I'd presume all APs would behave the same way, so no
need for lock management, or isolation between them.

- Justin