[PATCH 0/2] mm/mm_init: don't overlap zones with kernelcore=mirror

[PATCH 0/2] mm/mm_init: don't overlap zones with kernelcore=mirror

[Mike Rapoport]

From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>

Hi,

These patches make the behaviour of kernelcore= parameter uniform and
treat mirror just as another way to size the zones and cleanup a weird
part of the memory map initialization.
   
Mike Rapoport (Microsoft) (2):
  mm/mm_init: don't overlap NORMAL and MOVABLE zones with kernelcore=mirror
  mm/mm_init: drop overlap_memmap_init()

 mm/mm_init.c | 60 +++-------------------------------------------------
 1 file changed, 3 insertions(+), 57 deletions(-)


base-commit: 4549871118cf616eecdd2d939f78e3b9e1dddc48
-- 
2.53.0

[PATCH 1/2] mm/mm_init: don't overlap NORMAL and MOVABLE zones with kernelcore=mirror

[Mike Rapoport]

From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>

When kernelcore or movablecore kernel parameters define size of the
NORMAL and MOVABLE zones as percents of the total memory or by absolute
value, ZONE_NORMAL is clamped at the beginning of ZONE_MOVABLE.

However, when kernelcore=mirror the ZONE_NORMAL span is not changed but
rather pages from ZONE_MOVABLE counted as absent in ZONE_NORMAL.

Make the behaviour of kernelcore= parameter uniform and treat mirror
just as another way to size the zones.

Co-developed-by: Wei Yang <richard.weiyang@gmail.com>
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
---
 mm/mm_init.c | 36 +++---------------------------------
 1 file changed, 3 insertions(+), 33 deletions(-)

diff --git a/mm/mm_init.c b/mm/mm_init.c
index f9f8e1af921c..dce9dc9f2302 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -1159,9 +1159,8 @@ static void __init adjust_zone_range_for_zone_movable(int nid,
 				arch_zone_highest_possible_pfn[movable_zone]);
 
 		/* Adjust for ZONE_MOVABLE starting within this range */
-		} else if (!mirrored_kernelcore &&
-			*zone_start_pfn < zone_movable_pfn[nid] &&
-			*zone_end_pfn > zone_movable_pfn[nid]) {
+		} else if (*zone_start_pfn < zone_movable_pfn[nid] &&
+			   *zone_end_pfn > zone_movable_pfn[nid]) {
 			*zone_end_pfn = zone_movable_pfn[nid];
 
 		/* Check if this whole range is within ZONE_MOVABLE */
@@ -1209,40 +1208,11 @@ static unsigned long __init zone_absent_pages_in_node(int nid,
 					unsigned long zone_start_pfn,
 					unsigned long zone_end_pfn)
 {
-	unsigned long nr_absent;
-
 	/* zone is empty, we don't have any absent pages */
 	if (zone_start_pfn == zone_end_pfn)
 		return 0;
 
-	nr_absent = __absent_pages_in_range(nid, zone_start_pfn, zone_end_pfn);
-
-	/*
-	 * ZONE_MOVABLE handling.
-	 * Treat pages to be ZONE_MOVABLE in ZONE_NORMAL as absent pages
-	 * and vice versa.
-	 */
-	if (mirrored_kernelcore && zone_movable_pfn[nid]) {
-		unsigned long start_pfn, end_pfn;
-		struct memblock_region *r;
-
-		for_each_mem_region(r) {
-			start_pfn = clamp(memblock_region_memory_base_pfn(r),
-					  zone_start_pfn, zone_end_pfn);
-			end_pfn = clamp(memblock_region_memory_end_pfn(r),
-					zone_start_pfn, zone_end_pfn);
-
-			if (zone_type == ZONE_MOVABLE &&
-			    memblock_is_mirror(r))
-				nr_absent += end_pfn - start_pfn;
-
-			if (zone_type == ZONE_NORMAL &&
-			    !memblock_is_mirror(r))
-				nr_absent += end_pfn - start_pfn;
-		}
-	}
-
-	return nr_absent;
+	return __absent_pages_in_range(nid, zone_start_pfn, zone_end_pfn);
 }
 
 /*
-- 
2.53.0

Re: [PATCH 1/2] mm/mm_init: don't overlap NORMAL and MOVABLE zones with kernelcore=mirror

[David Hildenbrand (Arm)]

On 6/25/26 09:39, Mike Rapoport wrote:
> From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
> 
> When kernelcore or movablecore kernel parameters define size of the
> NORMAL and MOVABLE zones as percents of the total memory or by absolute
> value, ZONE_NORMAL is clamped at the beginning of ZONE_MOVABLE.
> 
> However, when kernelcore=mirror the ZONE_NORMAL span is not changed but
> rather pages from ZONE_MOVABLE counted as absent in ZONE_NORMAL.
> 
> Make the behaviour of kernelcore= parameter uniform and treat mirror
> just as another way to size the zones.

That sounds just about right to me.

Hard to imagine that any code would have relied on the old behavior.


Reviewed-by: David Hildenbrand (Arm) <david@kernel.org>

-- 
Cheers,

David

[PATCH 2/2] mm/mm_init: drop overlap_memmap_init()

[Mike Rapoport]

From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>

When ZONE_NORMAL and ZONE_MOVABLE could overlap because kernelcore=mirror
didn't reduce the span of ZONE_NORMAL, initialization of the memory map had
to skip overlapping pages during initialization of ZONE_MOVABLE to avoid
double initialization of the same struct pages.

Since kernelcore=mirror works now the same way as other variants of
kernelcore=/movablecore=, and adjusts the span of ZONE_NORMAL, there can't
be an overlap between ZONE_NORMAL and ZONE_MOVABLE.

Remove overlap_memmap_init().

Co-developed-by: Wei Yang <richard.weiyang@gmail.com>
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
---
 mm/mm_init.c | 24 ------------------------
 1 file changed, 24 deletions(-)

diff --git a/mm/mm_init.c b/mm/mm_init.c
index dce9dc9f2302..6f0a71ccca30 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;
-- 
2.53.0

Re: [PATCH 2/2] mm/mm_init: drop overlap_memmap_init()

[Wei Yang]

On Thu, Jun 25, 2026 at 10:39:40AM +0300, Mike Rapoport wrote:
>From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
>
>When ZONE_NORMAL and ZONE_MOVABLE could overlap because kernelcore=mirror
>didn't reduce the span of ZONE_NORMAL, initialization of the memory map had
>to skip overlapping pages during initialization of ZONE_MOVABLE to avoid
>double initialization of the same struct pages.
>
>Since kernelcore=mirror works now the same way as other variants of
>kernelcore=/movablecore=, and adjusts the span of ZONE_NORMAL, there can't
>be an overlap between ZONE_NORMAL and ZONE_MOVABLE.
>
>Remove overlap_memmap_init().
>

Hi, Mike

Do you think this is valuable to mention the double init for the overlapped
range?

>Co-developed-by: Wei Yang <richard.weiyang@gmail.com>
>Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
>Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
>---
> mm/mm_init.c | 24 ------------------------
> 1 file changed, 24 deletions(-)
>
>diff --git a/mm/mm_init.c b/mm/mm_init.c
>index dce9dc9f2302..6f0a71ccca30 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;
>-- 
>2.53.0

-- 
Wei Yang
Help you, Help me

Re: [PATCH 2/2] mm/mm_init: drop overlap_memmap_init()

[David Hildenbrand (Arm)]

On 6/25/26 09:39, Mike Rapoport wrote:
> From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
> 
> When ZONE_NORMAL and ZONE_MOVABLE could overlap because kernelcore=mirror
> didn't reduce the span of ZONE_NORMAL, initialization of the memory map had
> to skip overlapping pages during initialization of ZONE_MOVABLE to avoid
> double initialization of the same struct pages.
> 
> Since kernelcore=mirror works now the same way as other variants of
> kernelcore=/movablecore=, and adjusts the span of ZONE_NORMAL, there can't
> be an overlap between ZONE_NORMAL and ZONE_MOVABLE.
> 
> Remove overlap_memmap_init().
> 
> Co-developed-by: Wei Yang <richard.weiyang@gmail.com>
> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
> Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> ---

Reviewed-by: David Hildenbrand (Arm) <david@kernel.org>

-- 
Cheers,

David