linux-kernel - Re: Case: 7454422: Re: Kernel 2.6.21.3 does not work with 8GB of RAM on Intel 965WH motherboards. (FULL DMESG)

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Date:	Wed, 30 May 2007 17:29:17 -0600
From:	Robert Hancock <hancockr@...w.ca>
To:	Justin Piszcz <jpiszcz@...idpixels.com>
Cc:	linux-kernel@...r.kernel.org, crmotherboard@...lbox.intel.com
Subject: Re: Case: 7454422: Re: Kernel 2.6.21.3 does not work with 8GB of RAM
 on Intel 965WH motherboards. (FULL DMESG)

Justin Piszcz wrote:
> That output looked nasty, attaching entries from syslog.
> 
> Justin.

Here's your E820 memory map, from dmesg:

BIOS-e820: 0000000000000000 - 000000000008f000 (usable)
BIOS-e820: 000000000008f000 - 00000000000a0000 (reserved)
BIOS-e820: 00000000000e0000 - 0000000000100000 (reserved)
BIOS-e820: 0000000000100000 - 00000000cf58f000 (usable)
BIOS-e820: 00000000cf58f000 - 00000000cf59c000 (reserved)
BIOS-e820: 00000000cf59c000 - 00000000cf653000 (usable)
BIOS-e820: 00000000cf653000 - 00000000cf6a5000 (ACPI NVS)
BIOS-e820: 00000000cf6a5000 - 00000000cf6a8000 (ACPI data)
BIOS-e820: 00000000cf6a8000 - 00000000cf6ef000 (ACPI NVS)
BIOS-e820: 00000000cf6ef000 - 00000000cf6f1000 (ACPI data)
BIOS-e820: 00000000cf6f1000 - 00000000cf6f2000 (usable)
BIOS-e820: 00000000cf6f2000 - 00000000cf6ff000 (ACPI data)
BIOS-e820: 00000000cf6ff000 - 00000000cf700000 (usable)
BIOS-e820: 00000000cf700000 - 00000000d0000000 (reserved)
BIOS-e820: 00000000fff00000 - 0000000100000000 (reserved)
BIOS-e820: 0000000100000000 - 000000022c000000 (usable)

so the usable memory ranges are:

0-572K
1MB-3317.55MB
3317.60MB-3317.75MB
3318.94MB-3318.945MB
3318.996MB-3319MB
4096MB-8896MB

and the MTRRs (from /proc/mtrr, from private email):

reg00: base=0x00000000 (   0MB), size=2048MB: write-back, count=1
reg01: base=0x80000000 (2048MB), size=1024MB: write-back, count=1
reg02: base=0xc0000000 (3072MB), size= 256MB: write-back, count=1
reg03: base=0xcf800000 (3320MB), size=   8MB: uncachable, count=1
reg04: base=0xcf700000 (3319MB), size=   1MB: uncachable, count=1
reg05: base=0x100000000 (4096MB), size=4096MB: write-back, count=1
reg06: base=0x200000000 (8192MB), size= 512MB: write-back, count=1
reg07: base=0x220000000 (8704MB), size= 128MB: write-back, count=1

so the ranges mapped as cacheable are:

0-3319MB
4096-8832MB

leaving 64MB of memory at the top of RAM uncached. What do you want to
bet that something important (kernel code?) is getting loaded there..

So essentially it's a BIOS problem, it's not setting up the MTRRs
properly in order to map all of RAM as cacheable. As Andi says, complain
to Intel.

-- 
Robert Hancock      Saskatoon, SK, Canada
To email, remove "nospam" from hancockr@...pamshaw.ca
Home Page: http://www.roberthancock.com/

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