On 02/24/26 at 04:53pm, Jinjie Ruan wrote:
> 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.
>
> Crash kernel memory reservation wastes production resources if too
> large, risks kdump failure if too small, and faces allocation difficulties
> on fragmented systems due to contiguous block constraints. The new
> CMA-based crashkernel reservation scheme splits the "large fixed
> reservation" into a "small fixed region + large CMA dynamic region": the
> CMA memory is available to userspace during normal operation to avoid
> waste, and is reclaimed for kdump upon crash—saving memory while
> improving reliability.
>
> So extend crashkernel CMA reservation support to arm64. The following
> changes are made to enable CMA reservation:
>
> - 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 for kdump kernel to use.
> - Exclude the CMA-reserved ranges from the crash kernel memory to
> prevent them from being exported through /proc/vmcore, which is already
> done in the crash core.
>
> Update kernel-parameters.txt to document CMA support for crashkernel on
> arm64 architecture.
>
> Acked-by: Ard Biesheuvel <[email protected]>
> Signed-off-by: Jinjie Ruan <[email protected]>
> ---
> v3:
> - Add Acked-by.
> v2:
> - Free cmem in prepare_elf_headers()
> - Add the mtivation.
> ---
> Documentation/admin-guide/kernel-parameters.txt | 2 +-
> arch/arm64/kernel/machine_kexec_file.c | 8 +++++++-
> arch/arm64/mm/init.c | 5 +++--
> 3 files changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt
> b/Documentation/admin-guide/kernel-parameters.txt
> index cb850e5290c2..497f63b76898 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -1121,7 +1121,7 @@ Kernel parameters
> It will be ignored when crashkernel=X,high is not used
> or memory reserved is below 4G.
> crashkernel=size[KMG],cma
> - [KNL, X86, ppc] Reserve additional crash kernel memory
> from
> + [KNL, X86, ARM64, ppc] Reserve additional crash kernel
> memory from
~~~~
This should be written as 'PPC', even though it's not introduced in this patch.
===
PPC PowerPC architecture is enabled.
===
Other than this nit, the overral looks good to me.
> CMA. This reservation is usable by the first system's
> userspace memory and kernel movable allocations (memory
> balloon, zswap). Pages allocated from this memory range
......snip...
