linux-kernel - Re: How to tell kernel that a region of memory is reserved (in middle of ram)?

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Date:	Wed, 2 Jun 2010 13:31:29 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Maxim Levitsky <maximlevitsky@...il.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: How to tell kernel that a region of memory is reserved (in middle 
	of ram)?

On Wed, Jun 2, 2010 at 3:11 AM, Maxim Levitsky <maximlevitsky@...il.com> wrote:
> Hi,
>
> I need to reserve a region of ram to store there a ramoops buffer.
> I need to do so early so kernel doesn't overwrite the existing contents.
>
> How to do it?
>
> I noticed that doing memmap=20M$0x70000000 crashes the system although
> it promised to work.
> Is that a bug?
>
> I have 2GB system with following memory map:
>
> [    0.000000] BIOS-provided physical RAM map:
> [    0.000000]  BIOS-e820: 0000000000000000 - 000000000009fc00 (usable)
> [    0.000000]  BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved)
> [    0.000000]  BIOS-e820: 00000000000e0000 - 0000000000100000 (reserved)
> [    0.000000]  BIOS-e820: 0000000000100000 - 000000007fcfd000 (usable)
> [    0.000000]  BIOS-e820: 000000007fcfd000 - 000000007fd08000 (reserved)
> [    0.000000]  BIOS-e820: 000000007fd08000 - 000000007fd52000 (usable)
> [    0.000000]  BIOS-e820: 000000007fd52000 - 000000007fd55000 (reserved)
> [    0.000000]  BIOS-e820: 000000007fd55000 - 000000007fdbb000 (usable)
> [    0.000000]  BIOS-e820: 000000007fdbb000 - 000000007fdbf000 (reserved)
> [    0.000000]  BIOS-e820: 000000007fdbf000 - 000000007fe70000 (usable)
> [    0.000000]  BIOS-e820: 000000007fe70000 - 000000007febf000 (ACPI NVS)
> [    0.000000]  BIOS-e820: 000000007febf000 - 000000007ff00000 (ACPI data)
> [    0.000000]  BIOS-e820: 000000007ff00000 - 0000000080000000 (reserved)
> [    0.000000]  BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved)
> [    0.000000]  BIOS-e820: 00000000fec00000 - 00000000fec01000 (reserved)
> [    0.000000]  BIOS-e820: 00000000fed14000 - 00000000fed1a000 (reserved)
> [    0.000000]  BIOS-e820: 00000000fed1c000 - 00000000fed20000 (reserved)
> [    0.000000]  BIOS-e820: 00000000fee00000 - 00000000fee01000 (reserved)
> [    0.000000]  BIOS-e820: 00000000fff00000 - 0000000100000000 (reserved)
>

kernel version?

you could boot with "debug earlyprintk=ttyS0,115200" to get more info.

YH
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