Re: [PATCH v4 1/2] mm: move overlap memory map init check to memmap_init()

[Wei Yang]

On Wed, Apr 22, 2026 at 01:11:26AM +0000, Wei Yang wrote:
>On Tue, Apr 21, 2026 at 08:55:07AM -0400, Yuan Liu wrote:
>>Move the overlap memmap init check from memmap_init_range() into
>>memmap_init().
>>
>>When mirrored kernelcore is enabled, avoid memory map initialization
>>for overlap regions. There are two cases that may overlap: a mirror
>>memory region assigned to movable zone, or a non-mirror memory region
>>assigned to a non-movable zone but falling within the movable zone
>>range.
>>
>>Signed-off-by: Yuan Liu <yuan1.liu@xxxxxxxxx>
>>---
>> mm/mm_init.c | 37 +++++++++++++------------------------
>> 1 file changed, 13 insertions(+), 24 deletions(-)
>>
>>diff --git a/mm/mm_init.c b/mm/mm_init.c
>>index df34797691bd..2b5233060504 100644
>>--- a/mm/mm_init.c
>>+++ b/mm/mm_init.c
>>@@ -797,28 +797,6 @@ void __meminit reserve_bootmem_region(phys_addr_t start,
>> 	}
>> }
>> 
>>-/* If zone is ZONE_MOVABLE but memory is mirrored, it is an overlapped init */
>>-static bool __meminit
>>-overlap_memmap_init(unsigned long zone, unsigned long *pfn)
>>-{
>>-	static struct memblock_region *r;
>>-
>>-	if (mirrored_kernelcore && zone == ZONE_MOVABLE) {
>>-		if (!r || *pfn >= memblock_region_memory_end_pfn(r)) {
>>-			for_each_mem_region(r) {
>>-				if (*pfn < memblock_region_memory_end_pfn(r))
>>-					break;
>>-			}
>>-		}
>>-		if (*pfn >= memblock_region_memory_base_pfn(r) &&
>>-		    memblock_is_mirror(r)) {
>>-			*pfn = memblock_region_memory_end_pfn(r);
>>-			return true;
>>-		}
>>-	}
>>-	return false;
>>-}
>>-
>> /*
>>  * Only struct pages that correspond to ranges defined by memblock.memory
>>  * are zeroed and initialized by going through __init_single_page() during
>>@@ -905,8 +883,6 @@ void __meminit memmap_init_range(unsigned long size, int nid, unsigned long zone
>> 		 * function.  They do not exist on hotplugged memory.
>> 		 */
>> 		if (context == MEMINIT_EARLY) {
>>-			if (overlap_memmap_init(zone, &pfn))
>>-				continue;
>> 			if (defer_init(nid, pfn, zone_end_pfn)) {
>> 				deferred_struct_pages = true;
>> 				break;
>>@@ -971,6 +947,7 @@ static void __init memmap_init(void)
>> 
>> 	for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, &nid) {
>> 		struct pglist_data *node = NODE_DATA(nid);
>>+		struct memblock_region *r = &memblock.memory.regions[i];
>> 
>> 		for (j = 0; j < MAX_NR_ZONES; j++) {
>> 			struct zone *zone = node->node_zones + j;
>>@@ -978,6 +955,18 @@ static void __init memmap_init(void)
>> 			if (!populated_zone(zone))
>> 				continue;
>> 
>>+			if (mirrored_kernelcore) {
>>+				const bool is_mirror = memblock_is_mirror(r);
>>+				const bool is_movable_zone = (j == ZONE_MOVABLE);
>>+
>>+				if (is_mirror && is_movable_zone)
>>+					continue;
>>+
>>+				if (!is_mirror && !is_movable_zone &&
>>+				    start_pfn >= zone_movable_pfn[nid])
>>+					continue;
>
>IIUC, when mirrored_kernelcore is set but !memblock_has_mirror() or
>is_kdump_kernel(), zone_movable_pfn[nid] is kept to be 0.
>
>This means it will skip all memory regions.
>

Did some tests. When mirrored_kernelcore && !memblock_has_mirror(), which
means there is no is_mirror memblock. This will leave zone_movable_pfn[nid] 0.

So for all memory regions, the above logic will skip them.

Adjust the code as below, my local test could pass and kernel bootup as
expected.