linux-kernel - Re: mtrr madness

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Date:	Mon, 1 Sep 2008 10:25:33 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Robert Hancock" <hancockr@...w.ca>
Cc:	"Lukas Hejtmanek" <xhejtman@....muni.cz>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: mtrr madness

On Mon, Sep 1, 2008 at 10:19 AM, Robert Hancock <hancockr@...w.ca> wrote:
> Lukas Hejtmanek wrote:
>>
>> Hello,
>>
>> it seems that all linux kernels contain a bug with mtrr:
>>
>>  cat /proc/mtrr reg00: base=0x00000000 (   0MB), size=198656MB:
>> write-back, count=1
>> reg01: base=0x80000000 (2048MB), size=197120MB: write-back, count=1
>> reg02: base=0x9fc00000 (2556MB), size=196612MB: uncachable, count=1
>> reg03: base=0x100000000 (4096MB), size=200704MB: write-back, count=1
>> reg04: base=0x200000000 (8192MB), size=204800MB: write-back, count=1
>>
>> (watch the size)
>>
>> it is definitely  present in the kernels 2.6.16, 2.6.24, 2.6.25, 2.6.26.
>>
>> 198656 is 0x3080000000, the correct value would be 0x80000000, similarly
>> 197120 is 0x3020000000, the correct would be 0x20000000.
>
> Those are set up by the BIOS, so it would be what's at fault. I think we may
> be adding something to fix this up though?

the fix is in mainline already...,
Author: Yinghai Lu <yhlu.kernel@...il.com>
Date:   Thu Aug 21 20:24:24 2008 -0700

    x86: work around MTRR mask setting

please try 2.6.27-rc5...

YH
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