Re: [PATCH v7] powerpc/kdump: Add support for crashkernel CMA reservation

[Sourabh Jain <sourabhjain@linux.ibm.com>]

On 08/11/25 08:14, Ritesh Harjani (IBM) wrote:
> Sourabh Jain <sourabhjain@linux.ibm.com> writes:
>
>> Commit 35c18f2933c5 ("Add a new optional ",cma" suffix to the
>> crashkernel= command line option") and commit ab475510e042 ("kdump:
>> implement reserve_crashkernel_cma") added CMA support for kdump
>> crashkernel reservation.
>>
>> Extend crashkernel CMA reservation support to powerpc.
>>
> Yup, would be nice to see this support landing in powerpc!
>
>> The following changes are made to enable CMA reservation on powerpc:
>>
>> - Parse and obtain the CMA reservation size along with other crashkernel
>>    parameters
>> - Call reserve_crashkernel_cma() to allocate the CMA region for kdump
>> - Include the CMA-reserved ranges in the usable memory ranges for the
>>    kdump kernel to use.
>> - Exclude the CMA-reserved ranges from the crash kernel memory to
>>    prevent them from being exported through /proc/vmcore.
>>
>> With the introduction of the CMA crashkernel regions,
>> crash_exclude_mem_range() needs to be called multiple times to exclude
>> both crashk_res and crashk_cma_ranges from the crash memory ranges. To
>> avoid repetitive logic for validating mem_ranges size and handling
>> reallocation when required, this functionality is moved to a new wrapper
>> function crash_exclude_mem_range_guarded().
>>
>> To ensure proper CMA reservation, reserve_crashkernel_cma() is called
>> after pageblock_order is initialized.
>>
>> Update kernel-parameters.txt to document CMA support for crashkernel on
>> powerpc architecture.
>>
>> Cc: Baoquan he <bhe@redhat.com>
>> Cc: Jiri Bohac <jbohac@suse.cz>
>> Cc: Hari Bathini <hbathini@linux.ibm.com>
>> Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
>> Cc: Mahesh Salgaonkar <mahesh@linux.ibm.com>
>> Cc: Michael Ellerman <mpe@ellerman.id.au>
>> Cc: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
>> Cc: Shivang Upadhyay <shivangu@linux.ibm.com>
>> Cc: kexec@lists.infradead.org
>> Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>
>> ---
>> Changelog:
>>
>> v6 -> v7
>> https://lore.kernel.org/all/20251104132818.1724562-1-sourabhjain@linux.ibm.com/
>>   - declare crashk_cma_size static
>>
>> ---
>>   .../admin-guide/kernel-parameters.txt         |  2 +-
>>   arch/powerpc/include/asm/kexec.h              |  2 +
>>   arch/powerpc/kernel/setup-common.c            |  4 +-
>>   arch/powerpc/kexec/core.c                     | 10 ++++-
>>   arch/powerpc/kexec/ranges.c                   | 43 ++++++++++++++-----
>>   5 files changed, 47 insertions(+), 14 deletions(-)
> Although my reviewed by may not count much here since I am not deeply
> familiar with arch/powerpc/kexec/** part..
>
> But FWIW, the patch overall looks logical to me.
> Keeping cma reservation in setup_arch() is the right thing to do to
> avoid issues like these in past [1]. The error handling logic and the
> loop logic for handling CMA ranges also looks correct to me.
>
> So feel free to add:
> Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
>
> [1]: https://lore.kernel.org/linuxppc-dev/3ae208e48c0d9cefe53d2dc4f593388067405b7d.1729146153.git.ritesh.list@gmail.com/

Thanks for the Review Ritesh.

- Sourabh Jain