Re: [PATCH v5 1/5] mm: move mirrored memory overlap checking to the outer loop

[Wei Yang]

On Wed, May 20, 2026 at 05:34:53AM -0400, Yuan Liu wrote:
>Move the overlap memmap initialization check from memmap_init_range()
>to memmap_init(), and replace the per-PFN check with a memblock-based
>check.

The description is a little simple.

Even I know the purpose, I feel confused at the first glance.

>
>Reviewed-by: Wei Yang <richard.weiyang@xxxxxxxxx>
>Reviewed-by: Jason Zeng <jason.zeng@xxxxxxxxx>
>Signed-off-by: Yuan Liu <yuan1.liu@xxxxxxxxx>
>---
> mm/mm_init.c | 29 +++++------------------------
> 1 file changed, 5 insertions(+), 24 deletions(-)
>
>diff --git a/mm/mm_init.c b/mm/mm_init.c
>index f9f8e1af921c..24e103a402b0 100644
>--- a/mm/mm_init.c
>+++ b/mm/mm_init.c
>@@ -783,28 +783,6 @@ void __meminit init_deferred_page(unsigned long pfn, int nid)
> 	__init_deferred_page(pfn, nid);
> }
> 
>-/* 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 __meminitdata;
>-
>-	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
>@@ -891,8 +869,6 @@ 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;
>@@ -956,6 +932,7 @@ static void __init memmap_init(void)
> 	int i, j, zone_id = 0, nid;
> 
> 	for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, &nid) {
>+		struct memblock_region *r = &memblock.memory.regions[i];
> 		struct pglist_data *node = NODE_DATA(nid);
> 
> 		for (j = 0; j < MAX_NR_ZONES; j++) {
>@@ -964,6 +941,10 @@ static void __init memmap_init(void)
> 			if (!populated_zone(zone))
> 				continue;
> 
>+			if (mirrored_kernelcore && j == ZONE_MOVABLE &&
>+			    memblock_is_mirror(r))
>+				continue;
>+

So you have figured out the memory layout of mirror memory?

Would you mind elaborate?

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

-- 
Wei Yang
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