[PATCH v24 0/9] arm64: add kdump support

[mjaggi@caviumnetworks.com (Manish Jaggi)]

On 09/05/2016 01:45 PM, AKASHI Takahiro wrote:
> [Cc: Marc]
> 
> On Fri, Sep 02, 2016 at 06:23:25PM +0530, Manish Jaggi wrote:
>>
>>
>> On 08/31/2016 11:01 AM, AKASHI Takahiro wrote:
>>> Manish,
>>>
>>> Thank you for testing my kdump and reporting issues.
>>>
>>> On Wed, Aug 31, 2016 at 09:11:52AM +0530, Manish Jaggi wrote:
>>>> Hi Akashi,
>>>>
>>>> On 08/09/2016 07:22 AM, AKASHI Takahiro wrote:
>>>>> This patch series adds kdump support on arm64.
>>>>>
>>>>> To load a crash-dump kernel to the systems, a series of patches to
>>>>> kexec-tools, which have not yet been merged upstream, are needed.
>>>>> Please use my kdump patches [1].
>>>>>
>>>>> To examine vmcore (/proc/vmcore) on a crash-dump kernel, you can use
>>>>>   - crash utility (coming v7.1.6 or later) [2]
>>>>>     (Necessary patches have already been queued in the master.)
>>>>>
>>>>> [1] T.B.D.
>>>>> [2] https://github.com/crash-utility/crash.git
>>>>>
>>>>> Changes for v24 (Aug 9, 2016):
>>>>>   o Rebase to Linux-4.8-rc1
>>>>>   o Update descriptions about newly added DT proerties
>>>>>
>>>>> Changes for v23 (July 26, 2016):
>>>>>
>>>>>   o Move memblock_reserve() to a single place in reserve_crashkernel()
>>>>>   o Use  cpu_park_loop() in ipi_cpu_crash_stop()
>>>>>   o Always enforce ARCH_LOW_ADDRESS_LIMIT to the memory range of crash kernel
>>>>>   o Re-implement fdt_enforce_memory_region() to remove non-reserve regions
>>>>>     (for ACPI) from usable memory at crash kernel
>>>>>
>>>>> Changes for v22 (July 12, 2016):
>>>>>
>>>>>   o Export "crashkernel-base" and "crashkernel-size" via device-tree,
>>>>>     and add some descriptions about them in chosen.txt
>>>>>   o Rename "usable-memory" to "usable-memory-range" to avoid inconsistency
>>>>>     with powerpc's "usable-memory"
>>>>>   o Make cosmetic changes regarding "ifdef" usage
>>>>>   o Correct some wordings in kdump.txt
>>>>>
>>>>> Changes for v21 (July 6, 2016):
>>>>>
>>>>>   o Remove kexec patches.
>>>>>   o Rebase to arm64's for-next/core (Linux-4.7-rc4 based).
>>>>>   o Clarify the description about kvm in kdump.txt.
>>>>>
>>>>> See the following link [3] for older changes:
>>>>> [3]  http://lists.infradead.org/pipermail/linux-arm-kernel/2016-June/438780.html
>>>>>
>>>>> AKASHI Takahiro (8):
>>>>>   arm64: kdump: reserve memory for crash dump kernel
>>>>>   memblock: add memblock_cap_memory_range()
>>>>>   arm64: limit memory regions based on DT property, usable-memory-range
>>>>>   arm64: kdump: implement machine_crash_shutdown()
>>>>>   arm64: kdump: add kdump support
>>>>>   arm64: kdump: add VMCOREINFO's for user-space coredump tools
>>>>>   arm64: kdump: enable kdump in the arm64 defconfig
>>>>>   arm64: kdump: update a kernel doc
>>>>>
>>>>> James Morse (1):
>>>>>   Documentation: dt: chosen properties for arm64 kdump
>>>>>
>>>>>  Documentation/devicetree/bindings/chosen.txt |  45 ++++++
>>>>>  Documentation/kdump/kdump.txt                |  16 ++-
>>>>>  arch/arm64/Kconfig                           |  11 ++
>>>>>  arch/arm64/configs/defconfig                 |   1 +
>>>>>  arch/arm64/include/asm/hardirq.h             |   2 +-
>>>>>  arch/arm64/include/asm/kexec.h               |  41 +++++-
>>>>>  arch/arm64/include/asm/smp.h                 |   2 +
>>>>>  arch/arm64/kernel/Makefile                   |   1 +
>>>>>  arch/arm64/kernel/crash_dump.c               |  71 ++++++++++
>>>>>  arch/arm64/kernel/machine_kexec.c            |  67 ++++++++-
>>>>>  arch/arm64/kernel/setup.c                    |   7 +-
>>>>>  arch/arm64/kernel/smp.c                      |  63 +++++++++
>>>>>  arch/arm64/mm/init.c                         | 202 +++++++++++++++++++++++++++
>>>>>  include/linux/memblock.h                     |   1 +
>>>>>  mm/memblock.c                                |  28 ++++
>>>>>  15 files changed, 551 insertions(+), 7 deletions(-)
>>>>>  create mode 100644 arch/arm64/kernel/crash_dump.c
>>>>>
>>>> Couple of points
>>>> a) Just a note, while testing, the crashkernel reserved memory should be less than ARCH_LOW_ADDRESS_LIMIT (=arm64_dma_phys_limit).
>>>
>>> I think that this is a common mistake not only for kdump, but also
>>> for general kernels.
>>> Since request_standard_resources() calls alloc_bootmem_low(),
>>> the kernel will panic if any of usable "System RAM" is located
>>> above ARCH_LOW_ADDRESS_LIMIT.
>>> For kdump, using "crashkernel=SS" notation is a convenient way
>>> to avoid this issue.
>>>
>>>> b) Has anyone tested this on a SoC with Gicv3 ITS ?
>>>> Should the GICD/R be reset prior to switching to crash kernel ?
>>>> I am seeing lot of GICv3: RWP timeout, gone fishing while crash kernel boots.
>>>
>>> I've never seen this kind of messages.
>>> I usually do my testing on a fast model.
>>> "compatible" of interrupt-controller is "arm,gic-v3."
>>>
>> I suspect gic_cpu_pm_notifier is not being called on any of the cores prior to start of crash kernel.
>> We might have to call it explicitly.
> 
> I'm not sure that it is the cause, but anyway none of any cpu_pm_notifier's
> will be called at panic. That is the reason why "maxcpus=1" should be
> specified (for kdump on arm64).
> 
What I meant was that since cpu_pm_notifier is not called before crash kernel is started,
GIC Distributor/re-distributor/ITS is not set in quiescent state.
In my setup the GICD_CTRL[RWP] bit is not cleared in the crashkernels' distributor init function.
Marc what do you think?
> -Takahiro AKASHI
> 
>>> Thanks,
>>> -Takahiro AKASHI
>>>
>>>> Thanks,
>>>> Manish