NetBSD Problem Report #51053

From www@NetBSD.org  Thu Apr  7 14:55:46 2016
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Date: Thu,  7 Apr 2016 14:55:45 +0000 (UTC)
From: swiftgriggs@gmail.com
Reply-To: swiftgriggs@gmail.com
To: gnats-bugs@NetBSD.org
Subject: Enabling i386 PAE mode results in instant-crash upon boot
X-Send-Pr-Version: www-1.0

>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
>Last-Modified:  Fri Apr 08 23:50:01 +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:

>Audit-Trail:
From: matthew green <mrg@eterna.com.au>
To: gnats-bugs@NetBSD.org
Cc: port-i386-maintainer@netbsd.org, gnats-admin@netbsd.org,
    netbsd-bugs@netbsd.org
Subject: re: port-i386/51053: Enabling i386 PAE mode results in instant-crash upon boot
Date: Fri, 08 Apr 2016 03:37:56 +1000

 FWIW, the GENERIC_PAE kernel i commited to -current recently has
 been working for -current.  this is on a 16GB machine, so it was
 necessary for full operation (otherwise it boots with 3.5GB for
 the OS.)


 .mrg.

From: Swift Griggs <swiftgriggs@gmail.com>
To: gnats-bugs@NetBSD.org
Cc: 
Subject: re: port-i386/51053: Enabling i386 PAE mode results in instant-crash
 upon boot
Date: Thu, 7 Apr 2016 10:43:58 -0600 (MDT)

 On Thu, 7 Apr 2016, matthew green wrote:
 > FWIW, the GENERIC_PAE kernel i commited to -current recently has been
 > working for -current.  this is on a 16GB machine, so it was necessary for
 > full operation (otherwise it boots with 3.5GB for the OS.)

 Well, it might be that it's the 8GB alignment issue someone else also
 mentioned. If you have a machine with >8GB try it on that one. Also, I'll
 try a GENERIC kernel from -current too. 

 Thanks!

 -Swift 

From: matthew green <mrg@eterna.com.au>
To: gnats-bugs@NetBSD.org
Cc: port-i386-maintainer@netbsd.org, gnats-admin@netbsd.org,
    netbsd-bugs@netbsd.org, swiftgriggs@gmail.com
Subject: re: port-i386/51053: Enabling i386 PAE mode results in instant-crash upon boot
Date: Sat, 09 Apr 2016 09:48:36 +1000

 unfortunately, my system with 16GB ram boots a -7 i386 PAE kernel
 fine so the problem you're seeing i am not seeing.


 .mrg.

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