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From: Jung-uk Kim <jkim@FreeBSD.org>
To: Marko Zec <zec@icir.org>
Date: Thu, 3 Sep 2009 16:51:47 -0400
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Cc: svn-src-head@FreeBSD.org, svn-src-all@FreeBSD.org,
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Subject: Re: svn commit: r196769 - in head/sys: amd64/amd64 i386/i386
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On Thursday 03 September 2009 04:25 pm, Marko Zec wrote:
> On Wednesday 02 September 2009 18:02:48 Jung-uk Kim wrote:
> > Author: jkim
> > Date: Wed Sep  2 16:02:48 2009
> > New Revision: 196769
> > URL: http://svn.freebsd.org/changeset/base/196769
> >
> > Log:
> >   - Work around ACPI mode transition problem for recent NVIDIA
> > 9400M chipset based Intel Macs.  Since r189055, these platforms
> > started freezing when ACPI is being initialized for unknown
> > reason.  For these platforms, we just use the old PAT layout. 
> > Note this change is not enough to boot fully on these platforms
> > because of other problems but it makes debugging possible. Note
> > MacBook5,2 may be affected as well but it was not added here
> > because of lack of hardware to test.
> >   - Initialize PAT MSR fully instead of reading and modifying it
> > for safety.
>
> Perhaps I'm missing something, but I fail to understand what is the
> purpose / use of variable pat_tested here?

Without it, bad things may happen while APs are being initialized in 
SMP case.

Jung-uk Kim