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

From: Pratyush Anand <panand@redhat.com>
To: AKASHI Takahiro <takahiro.akashi@linaro.org>,
	catalin.marinas@arm.com, will.deacon@arm.com, vgoyal@redhat.com,
	hbabus@us.ibm.com
Cc: linaro-kernel@lists.linaro.org, geoff@infradead.org,
	kexec@lists.infradead.org, linux-kernel@vger.kernel.org,
	broonie@kernel.org, david.griego@linaro.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 0/5] arm64: add kdump support
Date: Wed, 01 Apr 2015 21:26:39 +0530	[thread overview]
Message-ID: <551C1537.2030009@redhat.com> (raw)
In-Reply-To: <1427358533-3754-1-git-send-email-takahiro.akashi@linaro.org>

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@2240M
> 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.

~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
>