Subject: Re: [PATCH v6 0/4] support reserving crashkernel above 4G on arm64 kdump

From: Chen Zhou <[email-masked]>
Date: Thu, 19 Dec 2019 10:56:25 +0800

Hi John,

On 2019/12/19 1:18, John Donnelly wrote:
> HI 
> 
> SEE INLINE ON A QUESTION :
> 
>> On Dec 17, 2019, at 8:07 PM, Chen Zhou <[email-masked]> wrote:
>>
>> Hi all,
>>
>> Friendly ping...
>>
>> On 2019/8/30 15:11, Chen Zhou wrote:
>>> I am busy with other things, so it was a long time before this version was
>>> released.
>>>
>>> This patch series enable reserving crashkernel above 4G in arm64.
>>>
>>> There are following issues in arm64 kdump:
>>> 1. We use crashkernel=X to reserve crashkernel below 4G, which will fail
>>> when there is no enough low memory.
>>> 2. Currently, crashkernel=Y@X can be used to reserve crashkernel above 4G,
>>> in this case, if swiotlb or DMA buffers are requierd, crash dump kernel
>>> will boot failure because there is no low memory available for allocation.
> 
>   
>       Can you elaborate when the boot failures may fail due to lacking  swiotlb or DMA buffers ? Are these related to certain adapters or specific  platforms  ? 
> 
>      I have not seen this when using   crashkernel=2024M@35GB . 
> 

For example, in my environment "Huawei TaiShan 2280",
we need to use mpt3sas driver in crash dump kernel for dumping vmcore.

mpt3sas driver needs to call dma_pool_alloc to allocate some pages,
if there is no DMA buffer, page allocation will fail, which leads to crash dump kernel boot failure,
like this:

[2019/12/19 9:12:41] [   12.403501] mpt3sas_cm0: diag reset: SUCCESS
[2019/12/19 9:12:41] [   12.456076] mpt3sas_cm0: reply_post_free pool: dma_pool_alloc failed
[2019/12/19 9:12:41] [   12.462515] pci 0004:48:00.0: can't derive routing for PCI INT A
[2019/12/19 9:12:41] [   12.468761] mpt3sas 0004:49:00.0: PCI INT A: no GSI
[2019/12/19 9:12:41] [   12.476348] mpt3sas_cm0: failure at drivers/scsi/mpt3sas/mpt3sas_scsih.c:10626/_scsih_probe()!
[2019/12/19 9:14:38] [ TIME ] Timed out waiting for device dev-di…b3\x2d890a\x2d2ead7df26f48.device.
[2019/12/19 9:14:38] [DEPEND] Dependency failed for Initrd Root Device.
[2019/12/19 9:14:38] [DEPEND] Dependency failed for /sysroot.
[2019/12/19 9:14:38] [DEPEND] Dependency failed for Initrd Root File System.
[2019/12/19 9:14:38] [DEPEND] Dependency failed for Reload Configuration from the Real Root.
[2019/12/19 9:14:38] [DEPEND] Dependency failed for File System C…40bae-9eb8-46b3-890a-2ead7df26f48.

Thanks,
Chen Zhou

> 
>>>
>>> To solve these issues, introduce crashkernel=X,low to reserve specified
>>> size low memory.
>>> Crashkernel=X tries to reserve memory for the crash dump kernel under
>>> 4G. If crashkernel=Y,low is specified simultaneously, reserve spcified
>>> size low memory for crash kdump kernel devices firstly and then reserve
>>> memory above 4G.
>>>
>>> When crashkernel is reserved above 4G in memory, that is, crashkernel=X,low
>>> is specified simultaneously, kernel should reserve specified size low memory
>>> for crash dump kernel devices. So there may be two crash kernel regions, one
>>> is below 4G, the other is above 4G.
>>> In order to distinct from the high region and make no effect to the use of
>>> kexec-tools, rename the low region as "Crash kernel (low)", and add DT property
>>> "linux,low-memory-range" to crash dump kernel's dtb to pass the low region.
>>>
>>> Besides, we need to modify kexec-tools:
>>> arm64: kdump: add another DT property to crash dump kernel's dtb(see [1])
>>>
>>> The previous changes and discussions can be retrieved from:
>>>
>>> Changes since [v5]
>>> - Move reserve_crashkernel_low() into kernel/crash_core.c.
>>> - Delete crashkernel=X,high.
>>> - Modify crashkernel=X,low.
>>> If crashkernel=X,low is specified simultaneously, reserve spcified size low
>>> memory for crash kdump kernel devices firstly and then reserve memory above 4G.
>>> In addition, rename crashk_low_res as "Crash kernel (low)" for arm64, and then
>>> pass to crash dump kernel by DT property "linux,low-memory-range".
>>> - Update Documentation/admin-guide/kdump/kdump.rst.
>>>
>>> Changes since [v4]
>>> - Reimplement memblock_cap_memory_ranges for multiple ranges by Mike.
>>>
>>> Changes since [v3]
>>> - Add memblock_cap_memory_ranges back for multiple ranges.
>>> - Fix some compiling warnings.
>>>
>>> Changes since [v2]
>>> - Split patch "arm64: kdump: support reserving crashkernel above 4G" as
>>> two. Put "move reserve_crashkernel_low() into kexec_core.c" in a separate
>>> patch.
>>>
>>> Changes since [v1]:
>>> - Move common reserve_crashkernel_low() code into kernel/kexec_core.c.
>>> - Remove memblock_cap_memory_ranges() i added in v1 and implement that
>>> in fdt_enforce_memory_region().
>>> There are at most two crash kernel regions, for two crash kernel regions
>>> case, we cap the memory range [min(regs[*].start), max(regs[*].end)]
>>> and then remove the memory range in the middle.
>>>
>>> [1]: https://urldefense.proofpoint.com/v2/url?u=http-3A__lists.infradead.org_pipermail_kexec_2019-2DAugust_023569.html&d=DwICAg&c=RoP1YumCXCgaWHvlZYR8PZh8Bv7qIrMUB65eapI_JnE&r=t2fPg9D87F7D8jm0_3CG9yoiIKdRg4qc_thBw4bzMhc&m=ZAC6UYbT-3qLR3Dvevd09m6neWWzGWSphuvXXlXow68&s=9tn9kUBabiuYhVtXauANSDGaISnCnHLYcAUQgsPBFxs&e= 
>>> [v1]: https://urldefense.proofpoint.com/v2/url?u=https-3A__lkml.org_lkml_2019_4_2_1174&d=DwICAg&c=RoP1YumCXCgaWHvlZYR8PZh8Bv7qIrMUB65eapI_JnE&r=t2fPg9D87F7D8jm0_3CG9yoiIKdRg4qc_thBw4bzMhc&m=ZAC6UYbT-3qLR3Dvevd09m6neWWzGWSphuvXXlXow68&s=F-lM7II2cuMF_sK3b6-QhSbWM3X-pI_WZEs0sZitS7A&e= 
>>> [v2]: https://urldefense.proofpoint.com/v2/url?u=https-3A__lkml.org_lkml_2019_4_9_86&d=DwICAg&c=RoP1YumCXCgaWHvlZYR8PZh8Bv7qIrMUB65eapI_JnE&r=t2fPg9D87F7D8jm0_3CG9yoiIKdRg4qc_thBw4bzMhc&m=ZAC6UYbT-3qLR3Dvevd09m6neWWzGWSphuvXXlXow68&s=5Y-S6sqMTklHkOQsNtjTX3C7pV05BjKLGhJVfMHEvDs&e= 
>>> [v3]: https://urldefense.proofpoint.com/v2/url?u=https-3A__lkml.org_lkml_2019_4_9_306&d=DwICAg&c=RoP1YumCXCgaWHvlZYR8PZh8Bv7qIrMUB65eapI_JnE&r=t2fPg9D87F7D8jm0_3CG9yoiIKdRg4qc_thBw4bzMhc&m=ZAC6UYbT-3qLR3Dvevd09m6neWWzGWSphuvXXlXow68&s=cWn4zSRQupaZ3jjz4eDvD-pNkoLyL_hsZoRx4yJoD0c&e= 
>>> [v4]: https://urldefense.proofpoint.com/v2/url?u=https-3A__lkml.org_lkml_2019_4_15_273&d=DwICAg&c=RoP1YumCXCgaWHvlZYR8PZh8Bv7qIrMUB65eapI_JnE&r=t2fPg9D87F7D8jm0_3CG9yoiIKdRg4qc_thBw4bzMhc&m=ZAC6UYbT-3qLR3Dvevd09m6neWWzGWSphuvXXlXow68&s=Nslk4RJKIyIuT0IoQoolXNjupEDXplPhQQwnTSoXNWE&e= 
>>> [v5]: https://urldefense.proofpoint.com/v2/url?u=https-3A__lkml.org_lkml_2019_5_6_1360&d=DwICAg&c=RoP1YumCXCgaWHvlZYR8PZh8Bv7qIrMUB65eapI_JnE&r=t2fPg9D87F7D8jm0_3CG9yoiIKdRg4qc_thBw4bzMhc&m=ZAC6UYbT-3qLR3Dvevd09m6neWWzGWSphuvXXlXow68&s=HJVAM6sCxV2DnNg5d4pw8WPqtkmQnKvztEmkSIgtQ5M&e= 
>>>
>>> Chen Zhou (4):
>>>  x86: kdump: move reserve_crashkernel_low() into crash_core.c
>>>  arm64: kdump: reserve crashkenel above 4G for crash dump kernel
>>>  arm64: kdump: add memory for devices by DT property, low-memory-range
>>>  kdump: update Documentation about crashkernel on arm64
>>>
>>> Documentation/admin-guide/kdump/kdump.rst       | 13 ++++-
>>> Documentation/admin-guide/kernel-parameters.txt | 12 ++++-
>>> arch/arm64/include/asm/kexec.h                  |  3 ++
>>> arch/arm64/kernel/setup.c                       |  8 ++-
>>> arch/arm64/mm/init.c                            | 61 +++++++++++++++++++++--
>>> arch/x86/include/asm/kexec.h                    |  3 ++
>>> arch/x86/kernel/setup.c                         | 65 +++----------------------
>>> include/linux/crash_core.h                      |  4 ++
>>> include/linux/kexec.h                           |  1 -
>>> kernel/crash_core.c                             | 65 +++++++++++++++++++++++++
>>> 10 files changed, 168 insertions(+), 67 deletions(-)
>>>
>>
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> 
> 
> .
> 

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