port-i386/51053: Enabling i386 PAE mode results in instant-crash upon boot

[swiftgriggs%gmail.com@localhost]

>Number:         51053
>Category:       port-i386
>Synopsis:       Enabling i386 PAE mode results in instant-crash upon boot
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-i386-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Apr 07 15:00:00 +0000 2016
>Originator:     Swift Griggs
>Release:        i386
>Organization:
>Environment:
NetBSD m83.parsec.com 7.0 NetBSD 7.0 (GENERIC.201509250726Z) i386
>Description:
PAE mode seems pretty much completely broken. I've simply taken the NetBSD 7.0 i386 GENERIC kernel, enabled PAE, then booted the new kernel. That results in an instant kernel panic. If you try to get a backtrace then it usually just reboots the machine. However, if you enable full debugging you can usually get one 'bt' in and the *second* thing you do in the debugger will cause an instant-reboot. 

I brought this up on the mailing list and someone mentioned they have the same problem with enabling PAE for Xen kernels, too. He said that it seemed to be related to the amount of RAM a system has and if that amount is divisible by 8. I initially had problems with a system with 24G of RAM. However, I also tested a system with 16G of RAM and got the same results. 

I use PAE mode with the i386 to run wine programs in a RAM disk. There is no wine port for AMD64.
>How-To-Repeat:
Enable PAE in the GENERIC kernel on a system with more than 8GB of RAM. Reboot the system and you'll get a panic. 
>Fix: