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From: Frans Pop <elendil@planet.nl>
To: "Yinghai Lu" <yhlu.kernel@gmail.com>
Subject: Re: [git head] Should X86_PAT really default to yes?
Date: Mon, 5 May 2008 18:55:04 +0200
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Cc: "Jesse Barnes" <jesse.barnes@intel.com>,
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On Sunday 04 May 2008, Yinghai Lu wrote:
> can you boot with pat=off and send out /proc/mtrr?

Hmmm. Is 'pat=off' supposed to do anything?

With a default boot I see:
kernel: Command line: root=/dev/mapper/main-root ro vga=791
[...]
kernel: x86 PAT enabled: cpu 1, old 0x7040600070406, new 0x7010600070106

And with 'pat=off' I get the same:
kernel: Command line: root=/dev/mapper/main-root ro vga=791 pat=off
[...]
kernel: x86 PAT enabled: cpu 1, old 0x7040600070406, new 0x7010600070106

Anyway, the info in /proc/mtrr is identical with and without the option, and 
is also identical to what I get with 2.6.25.1:

$ cat /proc/mtrr
reg00: base=0x00000000 (   0MB), size=2048MB: write-back, count=1
reg01: base=0x7f800000 (2040MB), size=   8MB: uncachable, count=1
reg02: base=0x7f700000 (2039MB), size=   1MB: uncachable, count=1
reg03: base=0x80000000 (2048MB), size= 256MB: write-combining, count=1

Cheers,
FJP