Subject: Re: [PATCH v3 09/11] arm64: kdump: exclude non-dumpable reserved memory regions from vmcore

From: Mike Rapoport <[email-masked]>
Date: Sat, 30 May 2026 19:25:22 +0300

On Fri, May 29, 2026 at 04:08:41PM +0100, Will Deacon wrote:
> On Wed, May 27, 2026 at 11:29:15AM +0800, Wandun Chen wrote:
> > From: Wandun Chen <[email-masked]>
> > 
> > Reserved memory regions are excluded from vmcore by default unless
> > marked dumpable. Honor the dumpable flag to filter out device firmware
> > regions (e.g., GPU, DSP, modem) reserved via device tree, since they
> > typically contain data not useful for kernel crash analysis and can
> > significantly increase vmcore size.
> > 
> > Use of_reserved_mem_kdump_exclude() to perform the exclusion, and
> > pre-size the crash_mem array via of_reserved_mem_kdump_nr_ranges().
> > 
> > Signed-off-by: Wandun Chen <[email-masked]>
> > Tested-by: Meijing Zhao <[email-masked]>
> > ---
> >  arch/arm64/kernel/machine_kexec_file.c | 6 ++++++
> >  1 file changed, 6 insertions(+)
> > 
> > diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
> > index e31fabed378a..1d65320c6ba4 100644
> > --- a/arch/arm64/kernel/machine_kexec_file.c
> > +++ b/arch/arm64/kernel/machine_kexec_file.c
> > @@ -17,6 +17,7 @@
> >  #include <linux/memblock.h>
> >  #include <linux/of.h>
> >  #include <linux/of_fdt.h>
> > +#include <linux/of_reserved_mem.h>
> >  #include <linux/slab.h>
> >  #include <linux/string.h>
> >  #include <linux/types.h>
> > @@ -51,6 +52,7 @@ static int prepare_elf_headers(void **addr, unsigned long *sz)
> >  	nr_ranges = 2; /* for exclusion of crashkernel region */
> >  	for_each_mem_range(i, &start, &end)
> >  		nr_ranges++;
> > +	nr_ranges += of_reserved_mem_kdump_nr_ranges();
> >  
> >  	cmem = kmalloc_flex(*cmem, ranges, nr_ranges);
> >  	if (!cmem)
> > @@ -75,6 +77,10 @@ static int prepare_elf_headers(void **addr, unsigned long *sz)
> >  			goto out;
> >  	}
> >  
> > +	ret = of_reserved_mem_kdump_exclude(cmem);
> > +	if (ret)
> > +		goto out;
> > +
> >  	ret = crash_prepare_elf64_headers(cmem, true, addr, sz);
> 
> This looks fine to me:
> 
> Acked-by: Will Deacon <[email-masked]>
> 
> Although I do wonder whether there's scope to consolidate some of the
> arch code here. Now that you have a helper for reserved memory, perhaps
> the core code could also handle the crashkernel reservation itself as
> well? If the arch code passed in its number of memory regions, the
> core code could take care of (a) allocating the crash_mem ranges array
> (b) excluding the crashkernel and (c) excluding the reserved regions
> (the part you have here).
> 
> Obviously that would be follow-up work, but the fact that you're having
> to apply basically the same diff to three architectures is a bit of a
> giveaway that this could benefit from some wider cleanup.

There are patches that move common code to kernel/crash_core.c:

https://lore.kernel.org/all/[email-masked]
 
Review from arch maintainers would be helpful there ;-)

> Will

-- 
Sincerely yours,
Mike.