UEFI/Linux: How to change physical memory map?

manu · March 17, 2019, 8:32pm

Hi all,

I currently run Linux on the Hikey960 board.
cat /proc/iomem gives me the following physical memory map:

00000000-1abfffff : System RAM
  00080000-00ecffff : Kernel code
  01040000-01218fff : Kernel data
1ad88000-201fffff : System RAM
20400000-31ffffff : System RAM
32101000-3dffffff : System RAM
40000000-89b7ffff : System RAM
89cc0000-ba64ffff : System RAM
ba650000-ba88ffff : reserved
ba890000-ba897fff : System RAM
ba898000-ba89bfff : reserved
ba89c000-bf85ffff : System RAM
bf860000-bf89ffff : reserved
bf8a0000-bf8affff : System RAM
bf8b0000-bf8fffff : reserved
bf900000-bfffffff : System RAM

Now I would like to change the memory map and remove some of the memory from Linux. If I understand correctly, the Linux kernel reads this information from the device tree files which are populated by the UEFI beforehand. (ARM-UEFI)

My question is, where exactly in the UEFI code is the memory map created and which file is used to populated it? How can I change the memory map?

Best,
manu

leo-yan · March 18, 2019, 2:12am

Please check below file, AFAIK, all memory banks are defined in this file in UEFI:

github.com

96boards-hikey/OpenPlatformPkg/blob/testing/hikey960_v1.3.4/Platforms/Hisilicon/HiKey960/Library/HiKey960Lib/HiKey960Mem.c

/** @file
*
*  Copyright (c) 2016-2017, Linaro Limited. All rights reserved.
*
*  This program and the accompanying materials
*  are licensed and made available under the terms and conditions of the BSD License
*  which accompanies this distribution.  The full text of the license may be found at
*  http://opensource.org/licenses/bsd-license.php
*
*  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
*  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
*
**/

#include <Library/ArmPlatformLib.h>
#include <Library/DebugLib.h>
#include <Library/HobLib.h>
#include <Library/PcdLib.h>
#include <Library/IoLib.h>
#include <Library/MemoryAllocationLib.h>

This file has been truncated. show original

manu · March 18, 2019, 5:55pm

Oh I see … the UEFI defines the ranges that are NOT available to Linux, this is why I couldn’t find the memory ranges.
Thank you for your help

leo-yan · March 19, 2019, 11:43am

@manu, you are welcome!