[PATCH v4 0/7] powerpc/fadump: Improvements and fixes for firmware-assisted dump.

Mahesh J Salgaonkar mahesh at linux.vnet.ibm.com
Fri Apr 20 15:04:10 AEST 2018

One of the primary issues with Firmware Assisted Dump (fadump) on Power
is that it needs a large amount of memory to be reserved. This reserved
memory is used for saving the contents of old crashed kernel's memory before
fadump capture kernel uses old kernel's memory area to boot. However, This
reserved memory area stays unused until system crash and isn't available
for production kernel to use.

Instead of setting aside a significant chunk of memory that nobody can use,
take advantage Linux kernel's Contiguous Memory Allocator (CMA) feature,
to reserve a significant chunk of memory that the kernel is prevented from
using , but applications are free to use it.

Patch 1 moves the metadata region to the start of the reserved area for easy
handling/detection of metadata region in second kernel.
Patch 4 implements the usage of CMA region to allow production kernel to
use that memory for applications usage, making fadump reservationless.
Patch 3, 6 and 7 fixes various fadump issues and bugs.

Changes in V4:
- patch 1: Make fadump compatible irrespective of kernel versions.
- patch 4: moved out of the series and been posted seperatly at
- Documentation update about CMA reservation.

Changes in V3:
- patch 1 & 2: move metadata region and documentation update.
- patch 7: Un-register the faudmp on kexec path


Mahesh Salgaonkar (7):
      powerpc/fadump: Move the metadata region to start of the reserved area.
      powerpc/fadump: Update documentation to reflect the metadata region movement.
      powerpc/fadump: un-register fadump on kexec path.
      powerpc/fadump: Reservationless firmware assisted dump
      powerpc/fadump: Update documentation to reflect CMA reservation.
      powerpc/fadump: throw proper error message on fadump registration failure.
      powerpc/fadump: Do not allow hot-remove memory from fadump reserved area.

 Documentation/powerpc/firmware-assisted-dump.txt |   43 ++-
 arch/powerpc/include/asm/fadump.h                |   11 +
 arch/powerpc/kernel/fadump.c                     |  343 +++++++++++++++++++---
 arch/powerpc/platforms/pseries/hotplug-memory.c  |    7 
 4 files changed, 343 insertions(+), 61 deletions(-)


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