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

[takahiro.akashi@linaro.org (AKASHI Takahiro)]

[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).

-Takahiro AKASHI

> > Thanks,
> > -Takahiro AKASHI
> > 
> >> Thanks,
> >> Manish