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

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Message-ID: <86802c440804261822p4df226det4c4323fdee91781c@mail.gmail.com>
Date:	Sat, 26 Apr 2008 18:22:51 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Andrew Morton" <akpm@...ux-foundation.org>
Cc:	"Ingo Molnar" <mingo@...e.hu>, "Andi Kleen" <ak@...e.de>,
	"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 3:56 AM, Andrew Morton
<akpm@...ux-foundation.org> 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.
>

the BIOS should have set memhole to 2048MB or 2560M instead of 1033MB

good mtrr should

>  reg00: base=0x00000000 (0MB), size=2048MB: write-back, count=1
>  reg01: base=0x100000000 (4096MB), size=2048MB: write-back, count=1

or

>  reg00: base=0x00000000 (0MB), size=2048MB: write-back, count=1
>  reg01: base=0x80000000 (2048MB), size=512MB: write-back, count=1
>  reg02: base=0x100000000 (4096MB), size=1024MB: write-back, count=1
>  reg03: base=0x140000000 (4096MB), size=512MB: write-back, count=1

so please talk to your HW esp CPU vendor to fix the BIOS problem.

AMD Rev F and Quadcore should get

>  reg00: base=0x00000000 (0MB), size=2048MB: write-back, count=1

or

>  reg00: base=0x00000000 (0MB), size=2048MB: write-back, count=1
>  reg01: base=0x80000000 (2048MB), size=512MB: write-back, count=1

because [4G, TOM2) is WB by default.

YH
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