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

[Wandun]

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  - No DT binding needed; linux,no-dump proposal withdrawn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