linux-kernel - Re: [PATCH] x86_32: trim memory by updating e820 v3

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Date:	Sat, 26 Apr 2008 18:05:39 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Gabriel C" <nix.or.die@...glemail.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"Andi Kleen" <andi@...stfloor.org>
Cc:	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Ingo Molnar" <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"Jesse Barnes" <jesse.barnes@...el.com>,
	"Mika Fischer" <mika.fischer@...pnet.de>, balajirrao@...il.com
Subject: Re: [PATCH] x86_32: trim memory by updating e820 v3

On Sat, Apr 26, 2008 at 5:56 AM, Gabriel C <nix.or.die@...glemail.com> wrote:
>
> Andrew Morton wrote:
>  > On Tue, 22 Jan 2008 16:23:20 -0800 Yinghai Lu <Yinghai.Lu@....COM> wrote:
>  >
>  >> [PATCH] x86_32: trim memory by updating e820 v3
>  >>
>  >> when mtrr is not covering all e820 table, need to trim the ram, need to update e820
>  >>
>  >> reuse some code for x86_64
>  >>
>  >> here need to add early_get_cap and use it in early_cpu_detect, and move mtrr_bp_init early
>  >>
>  >> need Justine to test with his special system with bug bios.
>  >>
>  >> Signed-off-by: Yinghai Lu <yinghai.lu@....com>
>  >
>  > Speaking of mtrr and e820....
>  >
>  > Could someone please take a peek at
>  > http://bugzilla.kernel.org/show_bug.cgi?id=10508 ?
>  >
>  > For some reason we seem to have turned this:
>  >
>  > [    0.000000]  BIOS-e820: 0000000000000000 - 000000000009f800 (usable)
>  > [    0.000000]  BIOS-e820: 000000000009f800 - 00000000000a0000 (reserved)
>  > [    0.000000]  BIOS-e820: 00000000000dc000 - 0000000000100000 (reserved)
>  > [    0.000000]  BIOS-e820: 0000000000100000 - 00000000bf6d0000 (usable)
>  > [    0.000000]  BIOS-e820: 00000000bf6d0000 - 00000000bf6e3000 (ACPI NVS)
>  > [    0.000000]  BIOS-e820: 00000000bf6e3000 - 00000000c0000000 (reserved)
>  > [    0.000000]  BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved)
>  > [    0.000000]  BIOS-e820: 00000000fec00000 - 00000000fec10000 (reserved)
>  > [    0.000000]  BIOS-e820: 00000000fed00000 - 00000000fed00400 (reserved)
>  > [    0.000000]  BIOS-e820: 00000000fed14000 - 00000000fed1a000 (reserved)
>  > [    0.000000]  BIOS-e820: 00000000fed1c000 - 00000000fed90000 (reserved)
>  > [    0.000000]  BIOS-e820: 00000000fee00000 - 00000000fee01000 (reserved)
>  > [    0.000000]  BIOS-e820: 00000000ff000000 - 0000000100000000 (reserved)
>  > [    0.000000]  BIOS-e820: 0000000100000000 - 0000000140000000 (usable)
>  >
>  > into this:
>  >
>  > reg00: base=0xc0000000 (3072MB), size=1024MB: uncachable, count=1
>  > reg01: base=0x00000000 ( 0MB), size=4096MB: write-back, count=1
>  > reg02: base=0x100000000 (4096MB), size=1024MB: write-back, count=1
>  > reg03: base=0xbf700000 (3063MB), size= 1MB: uncachable, count=1
>  > reg04: base=0xbf800000 (3064MB), size= 8MB: uncachable, count=1
>  >
>  > which screws up the X server's attempt to map the video memory at
>  > 0xd0000000.
>
>  I see that on my box with ASUS P5E-VM DO and 4G RAM.
>  It has an Q35 intel chipset and the intel card is set to use 256MB in BIOS.
>
>  I tested 2.6.{24*,25,25-next,25-latest-git} 32/64 bit.
>
>  Also I get the mtrr type mismatch message on 32 and 64 bit kernels.
>
>  ...
>
>  [    0.000000] BIOS-provided physical RAM map:
>  [    0.000000]  BIOS-e820: 0000000000000000 - 000000000009ec00 (usable)
>  [    0.000000]  BIOS-e820: 000000000009ec00 - 00000000000a0000 (reserved)
>  [    0.000000]  BIOS-e820: 00000000000e4000 - 0000000000100000 (reserved)
>  [    0.000000]  BIOS-e820: 0000000000100000 - 00000000cf550000 (usable)
>  [    0.000000]  BIOS-e820: 00000000cf550000 - 00000000cf55e000 (ACPI data)
>  [    0.000000]  BIOS-e820: 00000000cf55e000 - 00000000cf5e0000 (ACPI NVS)
>  [    0.000000]  BIOS-e820: 00000000cf5e0000 - 00000000cf600000 (reserved)
>
> [    0.000000]  BIOS-e820: 00000000fee00000 - 00000000fee01000 (reserved)
>  [    0.000000]  BIOS-e820: 00000000ffc00000 - 0000000100000000 (reserved)
>  [    0.000000]  BIOS-e820: 0000000100000000 - 000000012c000000 (usable)
>  ...
>
>  cat /proc/mtrr :
>
>  reg00: base=0xd0000000 (3328MB), size= 256MB: uncachable, count=1
>  reg01: base=0xe0000000 (3584MB), size= 512MB: uncachable, count=1
>  reg02: base=0x00000000 (   0MB), size=4096MB: write-back, count=1
>  reg03: base=0x100000000 (4096MB), size= 512MB: write-back, count=1
>  reg04: base=0x120000000 (4608MB), size= 128MB: write-back, count=1
>  reg05: base=0x128000000 (4736MB), size=  64MB: write-back, count=1
>  reg06: base=0xcf600000 (3318MB), size=   2MB: uncachable, count=1
>
>
>  dmesg is saying :
>
>  ..
>
>  [   24.012694] [drm] Initialized i915 1.6.0 20060119 on minor 0
>  [   24.175500] mtrr: type mismatch for d0000000,10000000 old: write-back new: write-combining
>  [   24.423740] set status page addr 0x00033000

another continuous MTRR mapping.

several months ago, we were talking about modifying MTRR. but Eric
said that is not safe because acpi and smi...

YH
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