linux-kernel - [PATCH 0/2] Export kdump crashkernel CMA ranges

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Message-ID: <20251103035859.1267318-1-sourabhjain@linux.ibm.com>
Date: Mon,  3 Nov 2025 09:28:57 +0530
From: Sourabh Jain <sourabhjain@...ux.ibm.com>
To: linux-kernel@...r.kernel.org
Cc: Sourabh Jain <sourabhjain@...ux.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>, Baoquan he <bhe@...hat.com>,
        Jiri Bohac <jbohac@...e.cz>, Shivang Upadhyay <shivangu@...ux.ibm.com>,
        linuxppc-dev@...ts.ozlabs.org, kexec@...ts.infradead.org
Subject: [PATCH 0/2] Export kdump crashkernel CMA ranges

/sys/kernel/kexec_crash_cma_ranges to export all CMA regions reserved
for the crashkernel to user-space. This enables user-space tools
configuring kdump to determine the amount of memory reserved for the
crashkernel. When CMA is used for crashkernel allocation, tools can use
this information to warn users that attempting to capture user pages
while CMA reservation is active may lead to unreliable or incomplete
dump capture.

While adding documentation for the new sysfs interface, I realized that
there was no ABI document for the existing kexec and kdump sysfs
interfaces, so I added one.

The first patch adds the ABI documentation for the existing kexec and
kdump sysfs interfaces, and the second patch adds the
/sys/kernel/kexec_crash_cma_ranges sysfs interface along with its
corresponding ABI documentation.

*Seeking opinions*
There are already four kexec/kdump sysfs entries under /sys/kernel/,
and this patch series adds one more. Should we consider moving them to
a separate directory, such as /sys/kernel/kexec, to avoid polluting
/sys/kernel/? For backward compatibility, we can create symlinks at
the old locations for sometime and remove them in the future.

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Baoquan he <bhe@...hat.com>
Cc: Jiri Bohac <jbohac@...e.cz>
Cc: Shivang Upadhyay <shivangu@...ux.ibm.com>
Cc: linuxppc-dev@...ts.ozlabs.org
Cc: kexec@...ts.infradead.org

Sourabh Jain (2):
  Documentation/ABI: add kexec and kdump sysfs interface
  crash: export crashkernel CMA reservation to userspace

 .../ABI/testing/sysfs-kernel-kexec-kdump      | 53 +++++++++++++++++++
 kernel/ksysfs.c                               | 17 ++++++
 2 files changed, 70 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-kernel-kexec-kdump

-- 
2.51.0