Re: [PATCH v6 06/10] memblock: introduce MEMBLOCK_NODUMP flag

[Baoquan He <baoquan.he@linux.dev>]

On 09/02/26 at 03:31pm, Wandun Chen wrote:
> From: Wandun Chen <chenwandun@lixiang.com>
> 
> Add MEMBLOCK_NODUMP to mark regions that should be excluded from
> kdump vmcores.
> 
> The flag is meant for reserved memory that carries no data useful for
> crash analysis. Reusable reserved regions such as CMA may hold useful
> data, so these regions must not be marked MEMBLOCK_NODUMP. Subsequent
> patches wire this up for /reserved-memory and /memreserve/ entries.
> 
> Suggested-by: Rob Herring <robh@kernel.org>
> Signed-off-by: Wandun Chen <chenwandun@lixiang.com>
> Tested-by: Meijing Zhao <zhaomeijing@lixiang.com>
> ---
>  include/linux/memblock.h |  9 +++++++++
>  mm/memblock.c            | 16 ++++++++++++++++
>  2 files changed, 25 insertions(+)
> 
> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> index d62db9e776cf..b2fcf11fba2b 100644
> --- a/include/linux/memblock.h
> +++ b/include/linux/memblock.h
> @@ -52,6 +52,8 @@ extern unsigned long long max_possible_pfn;
>   * kernel that we know is good to use. It is the only memory that
>   * allocations may happen from in this phase.
>   * @MEMBLOCK_RSRV_HUGETLB: memory is reserved for hugetlb pages
> + * @MEMBLOCK_NODUMP: exclude from kdump vmcore. It carries no data useful
> + * for crash analysis (e.g. firmware carveouts).
>   */
>  enum memblock_flags {
>  	MEMBLOCK_NONE		= 0x0,	/* No special request */
> @@ -63,6 +65,7 @@ enum memblock_flags {
>  	MEMBLOCK_RSRV_KERN	= 0x20,	/* memory reserved for kernel use */
>  	MEMBLOCK_KHO_SCRATCH	= 0x40,	/* scratch memory for kexec handover */
>  	MEMBLOCK_RSRV_HUGETLB	= 0x80, /* memory reserved for hugetlb pages */
> +	MEMBLOCK_NODUMP		= 0x100,/* exclude from kdump vmcore */
>  };
>  
>  /**
> @@ -160,6 +163,7 @@ int memblock_reserved_mark_noinit(phys_addr_t base, phys_addr_t size);
>  int memblock_reserved_mark_kern(phys_addr_t base, phys_addr_t size);
>  int memblock_mark_kho_scratch(phys_addr_t base, phys_addr_t size);
>  int memblock_clear_kho_scratch(phys_addr_t base, phys_addr_t size);
> +int memblock_mark_nodump(phys_addr_t base, phys_addr_t size);
>  
>  void memblock_free(void *ptr, size_t size);
>  void reset_all_zones_managed_pages(void);
> @@ -306,6 +310,11 @@ static inline bool memblock_is_kho_scratch(struct memblock_region *m)
>  	return m->flags & MEMBLOCK_KHO_SCRATCH;
>  }
>  
> +static inline bool memblock_is_nodump(struct memblock_region *m)
> +{
> +	return m->flags & MEMBLOCK_NODUMP;
> +}
> +
>  int memblock_search_pfn_nid(unsigned long pfn, unsigned long *start_pfn,
>  			    unsigned long  *end_pfn);
>  void __next_mem_pfn_range(int *idx, int nid, unsigned long *out_start_pfn,
> diff --git a/mm/memblock.c b/mm/memblock.c
> index f2952d725c10..2e87f39826dd 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -1204,6 +1204,21 @@ __init int memblock_clear_kho_scratch(phys_addr_t base, phys_addr_t size)
>  				    MEMBLOCK_KHO_SCRATCH);
>  }
>  
> +/**
> + * memblock_mark_nodump - Mark a memory region with flag MEMBLOCK_NODUMP.
> + * @base: the base phys addr of the region
> + * @size: the size of the region
> + *
> + * Mark the region as not to be included in crash dumps.
> + *
> + * Return: 0 on success, -errno on failure.
> + */
> +int __init_memblock memblock_mark_nodump(phys_addr_t base, phys_addr_t size)
      ~~~~~~~~~~~~~~^
Is it impossible to use at runtime even thought it claims to be generic?


> +{
> +	return memblock_setclr_flag(&memblock.memory, base, size, 1,
> +				    MEMBLOCK_NODUMP);
> +}
> +
>  static bool should_skip_region(struct memblock_type *type,
>  			       struct memblock_region *m,
>  			       int nid, int flags)
> @@ -2887,6 +2902,7 @@ static const char * const flagname[] = {
>  	[ilog2(MEMBLOCK_RSRV_KERN)] = "RSV_KERN",
>  	[ilog2(MEMBLOCK_KHO_SCRATCH)] = "KHO_SCRATCH",
>  	[ilog2(MEMBLOCK_RSRV_HUGETLB)] = "RSV_HUGETLB",
> +	[ilog2(MEMBLOCK_NODUMP)] = "NODUMP",
>  };
>  
>  static int memblock_debug_show(struct seq_file *m, void *private)
> -- 
> 2.43.0
>