[PATCH v5] crash: export crashkernel CMA reservation to userspace

[Sourabh Jain]

On 17/11/25 23:12, Andrew Morton wrote:
> On Mon, 17 Nov 2025 09:49:05 +0530 Sourabh Jain <sourabhjain at linux.ibm.com> wrote:
>
>> Add a sysfs entry /sys/kernel/kexec/crash_cma_ranges to expose all
>> CMA crashkernel ranges.
>>
>> This allows userspace tools configuring kdump to determine how much
>> memory is reserved for crashkernel. If CMA is used, tools can warn
>> users when attempting to capture user pages with CMA reservation.
>>
>> The new sysfs hold the CMA ranges in below format:
>>
>> cat /sys/kernel/kexec/crash_cma_ranges
>> 100000000-10c7fffff
>>
>> There are already four kexec and kdump sysfs entries under /sys/kernel.
>> Adding more entries there would clutter the directory. To avoid this,
>> the new crash_cma_ranges sysfs entry is placed in a new kexec node under
>> /sys/kernel/.
> I suggest not creating /sys/kernel/kexec in this patch.
>
> Moving everything into a new /sys/kernel/kexec is a separate patchset
> and a separate concept and it might never be merged - it changes ABI!
>
> So let's put crash_cma_ranges in /sys/kernel and move it to
> /sys/kernel/kexec within the other patchset.

Yeah sure. I will send the patches accordingly.

Thanks,
Sourabh Jain