linux-kernel - mtrr failure, 3.1-rc1

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Message-Id: <20110825070335.3095B3BC183@tippex.mynet.homeunix.org>
Date:	Thu, 25 Aug 2011 09:03:35 +0200
From:	Anders Eriksson <aeriksson@...tmail.fm>
To:	torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
	aeriksson@...tmail.fm
Subject: mtrr failure, 3.1-rc1



My old P-II has 640MB ram, but the bios only sets up WC for the first 512, so i 
add this early in the boot process:
echo "base=0x20000000 size=0x8000000 type=write-back" > /proc/mtrr

For reasons I have forgot I also have to add 'disable_mtrr_check' to the 
command line. Works great.

As of merge dc43d9fa73d82083656fb9c02f4823bcdcfb9f91 This no longer works.
Adding that line to /proc/mtrr no longer has any effect (cat /proc/mtrr shows
only the reg00 entry).

Reverting that merge on top of rc3 brings things back to normal and /proc/mtrr 
shows:
reg00: base=0x000000000 (    0MB), size=  512MB, count=1: write-back
reg01: base=0x048000000 ( 1152MB), size=  128MB, count=1: write-combining
reg02: base=0x020000000 (  512MB), size=  128MB, count=2: write-back

Any ideas how to track this down futher? Would be good to get it fixed for 3.1

-Anders


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