README: important pmap update, port broken until it happens!

[Jason Thorpe <thorpej%nas.nasa.gov@localhost>]

Hi folks...

This is to warn you that the Amiga and Atari ports are going to break
as soon as I commit some other changes to sys/uvm; the fixes described
in this commit message address the problem that the m68k pmaps have
regarding these other UVM changes that I'm about to make.

I *would* have updated the Amiga and Atari pmaps, except they have
some structural differences that mean that the change isn't purely
mechanical to make (like the hp300, mvme68k, next68k, and x68k were;
I initially wrote and tested the changes on a 68040 Macintosh, since
I happen to have one of those in my office).

Two things need to happen:

        (1) The Amiga and Atari pmaps need to have a pmap_remove_mapping()
            function like the hp300, and need to use it in the same places
            that the hp300 pmap does.

        (2) The Amiga and Atari pmaps need to then integrate the rest of
            the change described in the commit message below (including
            revision numbers).

Until that happens, I would suggest that Amiga and Atari users NOT
track current as of tomorrow; I'll leave it up to the Amiga and
Atari portmasters to announce on their respecive mailing lists when
the port's pmap has been fixed.

------- Forwarded Message

Module Name:    syssrc
Committed By:   thorpej
Date:           Tue Jun 15 22:18:10 UTC 1999

Modified Files:

        syssrc/sys/arch/hp300/hp300: pmap.c
        syssrc/sys/arch/mac68k/mac68k: pmap.c
        syssrc/sys/arch/mvme68k/mvme68k: pmap.c
        syssrc/sys/arch/next68k/next68k: pmap.c
        syssrc/sys/arch/x68k/x68k: pmap.c

Log Message:

Don't (ab)use uvm_map_pageable() to allocate PT pages.  Instead, do
some internal reference counting on PT pages.  We still allocate them
with the page fault routine (a wire-fault, now), but no longer free
PT pages from pmap_pageable().


--
To generate a diff of this commit:
cvs rdiff -r1.74 -r1.75 syssrc/sys/arch/hp300/hp300/pmap.c
cvs rdiff -r1.57 -r1.58 syssrc/sys/arch/mac68k/mac68k/pmap.c
cvs rdiff -r1.33 -r1.34 syssrc/sys/arch/mvme68k/mvme68k/pmap.c
cvs rdiff -r1.14 -r1.15 syssrc/sys/arch/next68k/next68k/pmap.c
cvs rdiff -r1.37 -r1.38 syssrc/sys/arch/x68k/x68k/pmap.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.


------- End of Forwarded Message

        -- Jason R. Thorpe <thorpej%nas.nasa.gov@localhost>