Re: [PATCH 0/5] arm64: add kdump support

From: Pratyush Anand
Date: Wed Apr 01 2015 - 11:57:48 EST

Hi Akashi,

On Thursday 26 March 2015 01:58 PM, AKASHI Takahiro wrote:
This patch set enables kdump (crash dump kernel) support on arm64 on top of
Geoff's kexec patchset.

In this version, there are some arm64-specific usage/constraints:
1) "mem=" boot parameter must be specified on crash dump kernel
2) Kvm will not be enabled on crash dump kernel even if configured
See commit messages and Documentation/kdump/kdump.txt for details.

The only concern I have is whether or not we can use the exact same kernel
as both system kernel and crash dump kernel. The current arm64 kernel is
not relocatable in the exact sense but I have no problems in using the same
binary for testing kdump.

I tested the code with
- ATF v1.1 + EDK2(UEFI) v3.0-rc0
- kernel v4.0-rc4 + Geoff' kexec v8
on Base fast model, using my yet-to-be-submitted kexec-tools [1].
You may want to start a kernel with the following boot parameter:
and try
$ kexec -p --load <vmlinux> --append ...
$ echo c > /proc/sysrq-trigger

I tried to use your kdump patches for kernel and kexec-tools. I am not able to load the crash kernel properly.

I passed crashkernel=64M@259G (My 8GB RAM starts at 256G) to primary kernel.

Used following to load the crash kernel
kexec -p --load vmlinux --append="$( cat /proc/cmdline ) maxcpus=1 mem=64M reset_devices"

I see:

kexec_load failed: Cannot assign requested address
entry = 0x40c40005d0 flags = 0xb70001

What I noticed that arm64_load_other_segments does not calculate correct load address for purgatory or if I pass initrd then for that too within crash kernel allocated memory.

Shouldn't we have a function similar to locate_dtb_in_crashmem for putgatory as well as initrd? I can try to fix this allocation, but I was just wondering if I understood correctly or I am missing something.


To examine vmcore (/proc/vmcore), you may use
- gdb v7.7 or later
- crash + a small patch (to recognize v4.0 kernel)


AKASHI Takahiro (5):
arm64: kdump: reserve memory for crash dump kernel
arm64: kdump: implement machine_crash_shutdown()
arm64: kdump: do not go into EL2 before starting a crash dump kernel
arm64: add kdump support
arm64: enable kdump in the arm64 defconfig

Documentation/kdump/kdump.txt | 31 ++++++++++++++-
arch/arm64/Kconfig | 12 ++++++
arch/arm64/configs/defconfig | 1 +
arch/arm64/include/asm/kexec.h | 34 +++++++++++++++-
arch/arm64/kernel/Makefile | 1 +
arch/arm64/kernel/crash_dump.c | 71 +++++++++++++++++++++++++++++++++
arch/arm64/kernel/machine_kexec.c | 55 +++++++++++++++++++++++++-
arch/arm64/kernel/process.c | 7 +++-
arch/arm64/kernel/setup.c | 78 +++++++++++++++++++++++++++++++++++++
arch/arm64/kernel/smp.c | 10 ++++-
10 files changed, 294 insertions(+), 6 deletions(-)
create mode 100644 arch/arm64/kernel/crash_dump.c

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