Subject: Re: [PATCH 07/11] of: reserved_mem: add no-dump crash_mem exclusion helpers

From: Rob Herring <[email-masked]>
Date: Wed, 6 May 2026 09:50:22 -0500

On Wed, Apr 29, 2026 at 02:58:27PM +0800, Chen Wandun wrote:
> Provide two kdump-oriented helpers so that arch kexec_file code does
> not have to open-code the no-dump filtering loop:
> 
>  - of_reserved_mem_no_dump_nr_ranges() returns the number of reserved
>    regions flagged with linux,no-dump. Each exclusion may split one
>    existing crash_mem range into two, so callers use this count to
>    pre-size their crash_mem allocation.
> 
>  - of_reserved_mem_exclude_no_dump() walks the reserved_mem[] array
>    and calls crash_exclude_mem_range() for each no-dump region.
> 
> Both helpers are guarded by CONFIG_KEXEC_FILE; empty inline stubs are
> provided for the !KEXEC_FILE case so architecture code can call them
> unconditionally.
> 
> The consumers are added in the following arm64, riscv and loongarch
> patches in this series.
> 
> Signed-off-by: Chen Wandun <[email-masked]>
> Tested-by: Zhao Meijing <[email-masked]>
> ---
>  drivers/of/of_reserved_mem.c    | 54 +++++++++++++++++++++++++++++++++
>  include/linux/of_reserved_mem.h | 15 +++++++++
>  2 files changed, 69 insertions(+)
> 
> diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
> index 4b80420da2d2..038056a6408a 100644
> --- a/drivers/of/of_reserved_mem.c
> +++ b/drivers/of/of_reserved_mem.c
> @@ -27,6 +27,10 @@
>  
>  #include "of_private.h"
>  
> +#ifdef CONFIG_KEXEC_FILE
> +#include <linux/crash_core.h>
> +#endif

You shouldn't need ifdef around includes.

> +
>  static struct reserved_mem reserved_mem_array[MAX_RESERVED_REGIONS] __initdata;
>  static struct reserved_mem *reserved_mem __refdata = reserved_mem_array;
>  static int total_reserved_mem_cnt = MAX_RESERVED_REGIONS;
> @@ -916,6 +920,56 @@ struct reserved_mem *of_reserved_mem_lookup(struct device_node *np)
>  }
>  EXPORT_SYMBOL_GPL(of_reserved_mem_lookup);
>  
> +#ifdef CONFIG_KEXEC_FILE

Use 'if (IS_ENABLED())' within the function.

> +/**
> + * of_reserved_mem_no_dump_nr_ranges() - count reserved regions flagged
> + * with the linux,no-dump property.
> + *
> + * Each such region may split an existing crash_mem range into two when
> + * it is excluded, so callers can use this count to pre-size their
> + * crash_mem allocation.
> + */
> +unsigned int of_reserved_mem_no_dump_nr_ranges(void)
> +{
> +	unsigned int i, n = 0;
> +
> +	for (i = 0; i < reserved_mem_count; i++)
> +		if (reserved_mem[i].no_dump)
> +			n++;
> +	return n;
> +}
> +
> +/**
> + * of_reserved_mem_exclude_no_dump() - exclude no-dump reserved regions
> + * from a crash_mem list.
> + * @cmem: crash memory list to modify
> + *
> + * Walks the reserved_mem[] array and calls crash_exclude_mem_range() for
> + * every region with no_dump set. Intended to be called from arch kdump
> + * code when constructing the elfcorehdr.
> + *
> + * Returns 0 on success, or a negative error returned by
> + * crash_exclude_mem_range() on the first failure.
> + */
> +int of_reserved_mem_exclude_no_dump(struct crash_mem *cmem)
> +{
> +	unsigned int i;
> +	int ret;
> +
> +	for (i = 0; i < reserved_mem_count; i++) {
> +		struct reserved_mem *r = &reserved_mem[i];
> +
> +		if (!r->no_dump || !r->size)
> +			continue;
> +		ret = crash_exclude_mem_range(cmem, r->base,
> +					      r->base + r->size - 1);
> +		if (ret)
> +			return ret;
> +	}
> +	return 0;
> +}
> +#endif /* CONFIG_KEXEC_FILE */