linux-kernel - Re: [PATCH 2/3] pci: don't assume pref memio are 64bit -v2

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Date:	Sat, 18 Apr 2009 11:15:09 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Matthew Wilcox <matthew@....cx>, linux-pci@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] pci: don't assume pref memio are 64bit -v2


* Yinghai Lu <yinghai@...nel.org> wrote:

> one system with 4g installed ( there is 1g hole)
> 
> when 4G installed.
> BIOS put ACPI etc need the hole
> [    0.000000] BIOS-provided physical RAM map:
> [    0.000000]  BIOS-e820: 0000000000000000 - 000000000009bc00 (usable)
> [    0.000000]  BIOS-e820: 000000000009bc00 - 00000000000a0000 (reserved)
> [    0.000000]  BIOS-e820: 00000000000e3000 - 0000000000100000 (reserved)
> [    0.000000]  BIOS-e820: 0000000000100000 - 00000000bffa0000 (usable)
> [    0.000000]  BIOS-e820: 00000000bffa0000 - 00000000bffae000 (ACPI data)
> [    0.000000]  BIOS-e820: 00000000bffae000 - 00000000bfff0000 (ACPI NVS)
> [    0.000000]  BIOS-e820: 00000000bfff0000 - 00000000c0000000 (reserved)
> [    0.000000]  BIOS-e820: 00000000fee00000 - 00000000fee01000 (reserved)
> [    0.000000]  BIOS-e820: 00000000ffb00000 - 0000000100000000 (reserved)
> [    0.000000]  BIOS-e820: 0000000100000000 - 0000000140000000 (usable)
> so in kernel resource will be reserved for 0xbffa0000 - 0xbfff0000 for ACPI
> 0x100000 -  0xbffa0000 for RAM...

btw., sidenote, it would be nice to enhance the e820 table printout 
with size and hole info as well. I did this manually yesterday in 
another mail:

BIOS-provided physical RAM map:
 BIOS-e820: 0000000000000000 - 000000000009fc00 (usable)       0.639 MB RAM
 BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved)     0.001 MB
                                                [ hole ]       0.250 MB
 BIOS-e820: 00000000000e0000 - 0000000000100000 (reserved)     0.125 MB
 BIOS-e820: 0000000000100000 - 000000003ed94000 (usable)    1004.5   MB RAM
 BIOS-e820: 000000003ed94000 - 000000003ee4e000 (ACPI NVS)     0.7   MB
 BIOS-e820: 000000003ee4e000 - 000000003fea2000 (usable)      16.3   MB RAM
 BIOS-e820: 000000003fea2000 - 000000003fee9000 (ACPI NVS)     0.3   MB
 BIOS-e820: 000000003fee9000 - 000000003feed000 (usable)       0.15  MB RAM
 BIOS-e820: 000000003feed000 - 000000003feff000 (ACPI data     0.07  MB
 BIOS-e820: 000000003feff000 - 000000003ff00000 (usable)       0.004 MB RAM
                                                [ hole ]       1.0   MB
                                                [ hole ]    3072.0   MB

it would be extremely useful to have that in the printout, to see 
the physical address space layout at a glance. Small holes are easy 
to miss, and e820 entry sizes are hard to judge at a glance.

To make this fit well, i'd suggest to drop the 'BIOS-e820: ' prefix 
- it's redundant.

	Ingo
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