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

[Andrew Morton]

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.