PowerMacs with modern VM_MAX_KERNEL_ADDRESS for non-usefdt mode and usefdt mode (head -r345758 variant)

[Mark Millard]

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=233863
now has patches for head -r345758 which have all the
G3, G4, and G5 PowerMacs that I have access to (that
FreeBSD has ever been able to boot) operating for both:

A) the historical non-usefdt mode (openfirmware used live)
B) usefdt mode

using the modern VM_MAX_KERNEL_ADDRESS values.

I do not claim to have coded to FreeBSD source code
standards. The patches, as they are, are more for the
information they, and the various patch-attachment
notes, contain about what was a sufficient set of
changes. For parts of it, at least one other direction
of change would be an alternative.

I viewed generating the patches as investigatory for
the goal of "get PowerMacs going again for non-usefdt
mode --and usefdt mode", not as definitive of the best
form of change for getting them going.

As far as I know no one else has tested if the patches
work in their PowerMac context --or for any non-PowerMac
context for that matter. (Both are important but I'm
limited to old PowerMac's for powerpc64 and 32-bit
powerpc.)

I'm not sure what PowerMac's I'll have access to
fairly soon, possibly only one. Nor am I sure how
much time I'll have.

Hopefully the patches and their notes are of some
help if FreeBSD is to continue to officially support
PowerMacs.


Note:

In my personal environment I've set things up to use:

OK set nousefdt
OK boot

and default to usefdt mode, instead of using:

OK set usefdt
OK boot

and defaulting to openfirmware-used-live.

This change is not in the patches that I submitted.

===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)