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

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Message-ID: <aQrBbYVEQleExjpk@MiWiFi-R3L-srv>
Date: Wed, 5 Nov 2025 11:15:57 +0800
From: Baoquan he <bhe@...hat.com>
To: Sourabh Jain <sourabhjain@...ux.ibm.com>
Cc: linux-kernel@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>,
	Jiri Bohac <jbohac@...e.cz>,
	Shivang Upadhyay <shivangu@...ux.ibm.com>,
	linuxppc-dev@...ts.ozlabs.org, kexec@...ts.infradead.org
Subject: Re: [PATCH 0/2] Export kdump crashkernel CMA ranges

On 11/03/25 at 09:28am, Sourabh Jain wrote:
> /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.

That sounds a good idea, will you do it in v2? Because otherwise the
kexec_crash_cma_ranges need be moved too.


> 
> 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
>