Re: [PATCH] vmcoreinfo: export SECTION_HAS_MEM_MAP

["David Hildenbrand (Arm)" <david@kernel.org>]

On 9/28/26 12:23, Dave Young wrote:
> On 9/28/26 4:48 PM, David Hildenbrand (Arm) wrote:
>> The crash tool currently hardcodes SECTION_HAS_MEM_MAP, and makedumpfile
>> needs similar information (although still relying on
>> SECTION_MARKED_PRESENT, it should switch to SECTION_HAS_MEM_MAP).
>>
>> Let's just export the value instead, so tools that work on vmcoreinfo
>> will not have to guess.
>>
>> Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
>> ---
>> Result of the discussion in reply to "[PATCH v2 00/13] mm/sparse: remove
>> SECTION_MARKED_PRESENT and further cleanups" [1]
>>
>> This patch can go in independently. It would be preferable if both
>> go into the same kernel release ;)
>>
>> [1] https://lore.kernel.org/r/20260921-b4-sparsemem_cleanups-v2-0-54d81d65e125@kernel.org 
>> ---
>>  kernel/vmcore_info.c | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/kernel/vmcore_info.c b/kernel/vmcore_info.c
>> index 5a417f8a922a..7833a36064a8 100644
>> --- a/kernel/vmcore_info.c
>> +++ b/kernel/vmcore_info.c
>> @@ -182,6 +182,7 @@ static int __init crash_save_vmcoreinfo_init(void)
>>  	VMCOREINFO_STRUCT_SIZE(mem_section);
>>  	VMCOREINFO_OFFSET(mem_section, section_mem_map);
>>  	VMCOREINFO_NUMBER(SECTION_SIZE_BITS);
>> +	VMCOREINFO_NUMBER(SECTION_HAS_MEM_MAP);
>>  	VMCOREINFO_NUMBER(MAX_PHYSMEM_BITS);
>>  #endif
>>  	VMCOREINFO_STRUCT_SIZE(page);
> 
> Current crash code looks below:
> #define SECTION_MARKED_PRESENT          (1UL<<0)
> #define SECTION_HAS_MEM_MAP             (1UL<<1)
> #define SECTION_IS_ONLINE               (1UL<<2)
> #define SECTION_IS_EARLY                (1UL<<3)
> #define SECTION_TAINT_ZONE_DEVICE       (1UL<<4)
> #define SECTION_MAP_LAST_BIT            (1UL<<5)
> #define SECTION_MAP_MASK                (~(SECTION_MAP_LAST_BIT-1))
> 
> 
> And it does not match the kernel for below chunk with ifdef
> #ifdef CONFIG_ZONE_DEVICE
>         SECTION_TAINT_ZONE_DEVICE_BIT,
> #endif
> #ifdef CONFIG_SPARSEMEM_VMEMMAP_PREINIT
>         SECTION_IS_VMEMMAP_PREINIT_BIT,
> #endif
> 
> The last bit could be wrong in crash.  So all numbers should be exported in vmcoreinfo.
> 
> Thoughts?

You know the crash code best, so likely ... it's time one of the crash people
takes over this patch?

-- 
Cheers,

David