Re: [PATCH 05/11] of: reserved_mem: add linux,no-dump property support for reserved memory regions

From: Wandun <chenwandun1@gmail.com>
To: Rob Herring <robh@kernel.org>
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Subject: Re: [PATCH 05/11] of: reserved_mem: add linux,no-dump property support for reserved memory regions
Date: Thu, 7 May 2026 17:41:49 +0800	[thread overview]
Message-ID: <eece7690-634a-43c5-9b20-0afc174a89a0@gmail.com> (raw)
In-Reply-To: <20260506144542.GA2072596-robh@kernel.org>


On 5/6/26 22:45, Rob Herring wrote:
> On Wed, Apr 29, 2026 at 02:58:25PM +0800, Chen Wandun wrote:
>> Add a 'no_dump' field to struct reserved_mem and parse the
>> 'linux,no-dump' device tree property during reserved memory node
>> initialization. This property allows device tree authors to mark
>> specific reserved memory regions that should be excluded from kdump
>> vmcore dumps.
>>
>> Reserved memory regions used by device firmware (e.g., GPU, DSP, modem)
>> typically contain data that is not useful for kernel crash analysis and
>> can significantly increase vmcore size. The 'linux,no-dump' property
>> provides a declarative way to indicate these regions should be filtered
>> out when constructing the elfcorehdr for kdump.
>>
>> The property is named with a 'linux,' prefix because kdump/vmcore is
>> Linux-specific and the property is an OS hint rather than a hardware
>> description, matching existing properties such as 'linux,cma-default'
>> and 'linux,usable-memory-range'.
>>
>> The 'linux,no-dump' property is only effective when the region:
>>   - Does not have 'no-map': these regions are already excluded from
>>     vmcore since they are removed from the linear mapping (MEMBLOCK_NOMAP).
>>   - Does not have 'reusable': CMA reusable regions are actively used by
>>     the kernel for movable page allocations, and their contents are
>>     valuable for crash analysis.
>>
>> The no-dump status is also printed in the boot log alongside the
>> existing nomap and reusable flags for diagnostic purposes.
> I think this property is the wrong way around and probably not needed.
> The default should be exclude the regions, but if Linux is using the
> regions (like CMA) then it can decide on its own to include them.
>
> With the restructuring that went into 7.1, it should be possible for the
> CMA code (and code for any other regions) to set some flag for the
> region.
Agree that the property direction is wrong. Rework in v2:
   - Default: exclude reserved regions from vmcore
   - CMA (reusable) setup path marks regions as kernel-managed general 
memory → include
   - No DT binding needed; linux,no-dump proposal withdrawn

Thanks.
>
> Rob


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