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

[Ritesh Harjani (IBM)]

Sourabh Jain <sourabhjain at 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 at redhat.com>
> Cc: Jiri Bohac <jbohac at suse.cz>
> Cc: Hari Bathini <hbathini at linux.ibm.com>
> Cc: Madhavan Srinivasan <maddy at linux.ibm.com>
> Cc: Mahesh Salgaonkar <mahesh at linux.ibm.com>
> Cc: Michael Ellerman <mpe at ellerman.id.au>
> Cc: Ritesh Harjani (IBM) <ritesh.list at gmail.com>
> Cc: Shivang Upadhyay <shivangu at linux.ibm.com>
> Cc: kexec at lists.infradead.org
> Signed-off-by: Sourabh Jain <sourabhjain at 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 at gmail.com>

[1]: https://lore.kernel.org/linuxppc-dev/3ae208e48c0d9cefe53d2dc4f593388067405b7d.1729146153.git.ritesh.list@gmail.com/