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

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Message-ID: <1275473482.11579.21.camel@maxim-laptop>
Date:	Wed, 02 Jun 2010 13:11:22 +0300
From:	Maxim Levitsky <maximlevitsky@...il.com>
To:	linux-kernel <linux-kernel@...r.kernel.org>
Subject: How to tell kernel that a region of memory is reserved (in middle
 of ram)?

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)


Best regards,
	Maxim Levitsky

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