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

[Marc Zyngier <marc.zyngier@arm.com>]

On 05/09/16 13:42, Manish Jaggi wrote:
> 
> 
> 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.

Which is fine, they are not expected to be in a sane state anyway
(that's what a crash is about...). The ITS now has provision to be put
in a disabled state before being reinitialized. As for GICD, it is
disabled before being reprogrammed, which should be enough.

> In my setup the GICD_CTRL[RWP] bit is not cleared in the
> crashkernels' distributor init function.

Which instance is failing? The initial one (just after the initial
disable)? Or the one called from gic_dist_config()?

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...

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