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

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

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."

Thanks,
-Takahiro AKASHI

> Thanks,
> Manish