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

[Wandun <chenwandun1@gmail.com>]

On 9/18/26 16:08, Baoquan He wrote:
> 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?
It is currently only used during initialization, so I added __init_memblock.

If other modules need to use this function in the future, this annotation can
be removed.

Best regards,
Wandun>
> 
>> +{
>> +	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
>>