[PATCH v2 5/5] crash: export crashkernel CMA reservation to userspace

[Sourabh Jain]

On 06/11/25 10:21, Sourabh Jain 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
>
> Cc: Aditya Gupta <adityag at linux.ibm.com>
> Cc: Andrew Morton <akpm at linux-foundation.org>
> Cc: Baoquan he <bhe at redhat.com>
> Cc: Dave Young <dyoung at redhat.com>
> Cc: Hari Bathini <hbathini at linux.ibm.com>
> Cc: Jiri Bohac <jbohac at suse.cz>
> Cc: Madhavan Srinivasan <maddy at linux.ibm.com>
> Cc: Mahesh J Salgaonkar <mahesh at linux.ibm.com>
> Cc: Pingfan Liu <piliu at redhat.com>
> Cc: Ritesh Harjani (IBM) <ritesh.list at gmail.com>
> Cc: Shivang Upadhyay <shivangu at linux.ibm.com>
> Cc: Vivek Goyal <vgoyal at redhat.com>
> Cc: linuxppc-dev at lists.ozlabs.org
> Cc: kexec at lists.infradead.org
> Signed-off-by: Sourabh Jain <sourabhjain at linux.ibm.com>
> ---
>   Documentation/ABI/testing/sysfs-kernel-kexec-kdump | 10 ++++++++++
>   1 file changed, 10 insertions(+)
>
> diff --git a/Documentation/ABI/testing/sysfs-kernel-kexec-kdump b/Documentation/ABI/testing/sysfs-kernel-kexec-kdump
> index 00c00f380fea..f59051b5d96d 100644
> --- a/Documentation/ABI/testing/sysfs-kernel-kexec-kdump
> +++ b/Documentation/ABI/testing/sysfs-kernel-kexec-kdump
> @@ -49,3 +49,13 @@ Description:	read only
>   		is used by the user space utility kexec to support updating the
>   		in-kernel kdump image during hotplug operations.
>   User:		Kexec tools
> +
> +What:		/sys/kernel/kexec/crash_cma_ranges
> +Date:		Nov 2025
> +Contact:	kexec at lists.infradead.org
> +Description:	read only
> +		Provides information about the memory ranges reserved from
> +		the Contiguous Memory Allocator (CMA) area that are allocated
> +		to the crash (kdump) kernel. It lists the start and end physical
> +		addresses of CMA regions assigned for crashkernel use.
> +User:		kdump service
While rebasing the v1 patches, the hunk that adds the show function 
didn't get picked up.
I will send v3 with a show function to export the crashkernel CMA 
reservation.

- Sourabh Jain