linux-kernel - Re: [PATCH] x86: tidy e820 output

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Date:	Wed, 22 Sep 2010 12:20:33 -0600
From:	Bjorn Helgaas <bjorn.helgaas@...com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
	Yinghai Lu <yinghai@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: tidy e820 output

On Wednesday, September 22, 2010 11:54:49 am H. Peter Anvin wrote:
> On 09/22/2010 10:27 AM, Bjorn Helgaas wrote:
> > 
> > This tidies e820 output by adding an "e820" prefix and printing ranges in
> > the same style we use for struct resource with %pR, e.g.:
> > 
> >     - BIOS-e820: 0000000000000000 - 000000000009f400 (usable)
> >     + BIOS-e820: [mem 0x00000000-0x0009f3ff] (usable)
> 
> I'm sorry, I have to admit to not understanding the difference.  I do
> not want to change the number of hex digits from fixed 16 digits, as
> that will make the output harder to read when printed in a block (as is
> normal for the early e820 dump).  The [mem] prefix seems redundant with
> (usable), or am I misreading this?

These E820 ranges should be easily comparable with similar ranges we
print elsewhere.  Currently we have things like this:

    BIOS-e820: 0000000000000000 - 000000000009f400 (usable)
    BIOS-e820: 000000000009f400 - 00000000000a0000 (reserved)
    BIOS-e820: 00000000fffbc000 - 0000000100000000 (reserved)
    pci_root PNP0A03:00: host bridge window [mem 0x000a0000-0x000bffff]
    pci_root PNP0A03:00: host bridge window [mem 0xe0000000-0xfebfffff]
    pci 0000:00:02.0: reg 10: [mem 0xf0000000-0xf1ffffff pref]
    reserve RAM buffer: 000000000009f400 - 000000000009ffff 
    pnp 00:07: [mem 0xfed00000-0xfed003ff]

It would be easier to integrate the E820 information with the ACPI
and PCI window and BAR information if they looked similar.

We currently have a mix of some with "0x" prefix, some without;
some with eight hex digits, some with sixteen; some with spaces
around the internal "-", some without; some with type (io/mem/etc),
some without; some with uppercase hex (MTRR), most with lowercase;
some including the end address, some not; and even some in PFNs
and most in addresses.  It just makes it harder than it needs
to be to debug issues in this area.

Bjorn
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