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

[Wei Yang <richard.weiyang@gmail.com>]

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@intel.com>
>---
> 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.

>+			}
>+
> 			memmap_init_zone_range(zone, start_pfn, end_pfn,
> 					       &hole_pfn);
> 			zone_id = j;
>-- 
>2.47.3

-- 
Wei Yang
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