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

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Message-ID: <551C7EF5.9030806@linaro.org>
Date:	Thu, 02 Apr 2015 08:27:49 +0900
From:	AKASHI Takahiro <takahiro.akashi@...aro.org>
To:	Pratyush Anand <panand@...hat.com>, catalin.marinas@....com,
	will.deacon@....com, vgoyal@...hat.com, hbabus@...ibm.com
CC:	linaro-kernel@...ts.linaro.org, geoff@...radead.org,
	kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
	broonie@...nel.org, david.griego@...aro.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 0/5] arm64: add kdump support

Hi Pratyush,

On 04/02/2015 12:56 AM, Pratyush Anand wrote:
> 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:
>>     crashkernel=64M@...0M
>> 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@...G (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.

It seems that you hit the same problem that I mentioned in:
   http://lists.infradead.org/pipermail/linux-arm-kernel/2015-March/334613.html

Please try my latest kexec-tools in my linaro repo (branch name is kdump/v0.11)
and let me know the result.

> 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.

I don't think a function for purgatory is necessary since we try to find a hole
just after dtb.

Thanks,
-Takahiro AKASHI

> ~Pratyush
>
>
>> To examine vmcore (/proc/vmcore), you may use
>>     - gdb v7.7 or later
>>     - crash + a small patch (to recognize v4.0 kernel)
>>
>> [1] https://git.linaro.org/people/takahiro.akashi/kexec-tools.git
>>
>>
>> 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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