[PATCH v9 0/3] kho: add support for deferred struct page init

[PATCH v9 0/3] kho: add support for deferred struct page init

[Michal Clapinski]

When CONFIG_DEFERRED_STRUCT_PAGE_INIT is enabled, struct page
initialization is deferred to parallel kthreads that run later in
the boot process.

Currently, KHO is incompatible with DEFERRED.
This series fixes that incompatibility.
---
v9:
- moved init_pageblock_migratetype from memmap_init_reserved_range
  to __init_page_from_nid
- reduced number of ifdefs
- new commit to test this feature
v8:
- moved overriding the migratetype from init_pageblock_migratetype
  to callsites
v7:
- reimplemented the initialization of kho scratch again
v6:
- reimplemented the initialization of kho scratch
v5:
- rebased
v4:
- added a new commit to fix deferred init of kho scratch
- switched to ulong when refering to pfn
v3:
- changed commit msg
- don't invoke early_pfn_to_nid if CONFIG_DEFERRED_STRUCT_PAGE_INIT=n
v2:
- updated a comment

I took Evangelos's test code:
https://git.infradead.org/?p=users/vpetrog/linux.git;a=shortlog;h=refs/heads/kho-deferred-struct-page-init
and then modified it to this monster test that does 2 allocations:
at core_initcall (early) and at module_init (late). Then kexec, then
2 more allocations at these points, then restore the original 2, then
kexec, then restore the other 2. Basically I test preservation of early
and late allocation both on cold and on warm boot.
Tested it both with and without DEFERRED.
https://github.com/mclapinski/linux/commits/deferred_test/

This patch probably doesn't apply onto anything currently.
It's based on mm-new with
"memblock: move reserve_bootmem_range() to memblock.c and make it static"
cherrypicked from rppt/memblock.

Evangelos Petrongonas (1):
  kho: make preserved pages compatible with deferred struct page init

Michal Clapinski (2):
  kho: fix deferred initialization of scratch areas
  selftests: kho: test with deferred struct page init

 include/linux/memblock.h              | 21 +++++++++-
 kernel/liveupdate/Kconfig             |  2 -
 kernel/liveupdate/kexec_handover.c    | 52 ++++++++++++-------------
 mm/memblock.c                         | 56 +++++++++++----------------
 mm/mm_init.c                          | 30 +++++++-------
 tools/testing/selftests/kho/vmtest.sh |  4 ++
 6 files changed, 88 insertions(+), 77 deletions(-)

-- 
2.54.0.rc2.533.g4f5dca5207-goog

[PATCH v9 1/3] kho: fix deferred initialization of scratch areas

[Michal Clapinski]

Currently, if CONFIG_DEFERRED_STRUCT_PAGE_INIT is enabled,
kho_release_scratch() will initialize the struct pages and set migratetype
of KHO scratch. Unless the whole scratch fits below first_deferred_pfn,
some of that will be overwritten either by deferred_init_pages() or
memmap_init_reserved_range().

To fix it, make memmap_init_range(), deferred_init_memmap_chunk() and
__init_page_from_nid() recognize KHO scratch regions and set
migratetype of pageblocks in those regions to MIGRATE_CMA.

Co-developed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Michal Clapinski <mclapinski@google.com>
---
 include/linux/memblock.h           | 21 +++++++++--
 kernel/liveupdate/kexec_handover.c | 25 -------------
 mm/memblock.c                      | 56 ++++++++++++------------------
 mm/mm_init.c                       | 30 +++++++++-------
 4 files changed, 58 insertions(+), 74 deletions(-)

diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index b0f750d22a7b..5afcd99aa8c1 100644
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h
@@ -613,11 +613,28 @@ static inline void memtest_report_meminfo(struct seq_file *m) { }
 #ifdef CONFIG_MEMBLOCK_KHO_SCRATCH
 void memblock_set_kho_scratch_only(void);
 void memblock_clear_kho_scratch_only(void);
-void memmap_init_kho_scratch_pages(void);
+bool memblock_is_kho_scratch_memory(phys_addr_t addr);
+
+static inline enum migratetype kho_scratch_migratetype(unsigned long pfn,
+						       enum migratetype mt)
+{
+	if (memblock_is_kho_scratch_memory(PFN_PHYS(pfn)))
+		return MIGRATE_CMA;
+	return mt;
+}
 #else
 static inline void memblock_set_kho_scratch_only(void) { }
 static inline void memblock_clear_kho_scratch_only(void) { }
-static inline void memmap_init_kho_scratch_pages(void) {}
+static inline bool memblock_is_kho_scratch_memory(phys_addr_t addr)
+{
+	return false;
+}
+
+static inline enum migratetype kho_scratch_migratetype(unsigned long pfn,
+						       enum migratetype mt)
+{
+	return mt;
+}
 #endif
 
 #endif /* _LINUX_MEMBLOCK_H */
diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c
index 18509d8082ea..a507366a2cf9 100644
--- a/kernel/liveupdate/kexec_handover.c
+++ b/kernel/liveupdate/kexec_handover.c
@@ -1576,35 +1576,10 @@ static __init int kho_init(void)
 }
 fs_initcall(kho_init);
 
-static void __init kho_release_scratch(void)
-{
-	phys_addr_t start, end;
-	u64 i;
-
-	memmap_init_kho_scratch_pages();
-
-	/*
-	 * Mark scratch mem as CMA before we return it. That way we
-	 * ensure that no kernel allocations happen on it. That means
-	 * we can reuse it as scratch memory again later.
-	 */
-	__for_each_mem_range(i, &memblock.memory, NULL, NUMA_NO_NODE,
-			     MEMBLOCK_KHO_SCRATCH, &start, &end, NULL) {
-		ulong start_pfn = pageblock_start_pfn(PFN_DOWN(start));
-		ulong end_pfn = pageblock_align(PFN_UP(end));
-		ulong pfn;
-
-		for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages)
-			init_pageblock_migratetype(pfn_to_page(pfn),
-						   MIGRATE_CMA, false);
-	}
-}
-
 void __init kho_memory_init(void)
 {
 	if (kho_in.scratch_phys) {
 		kho_scratch = phys_to_virt(kho_in.scratch_phys);
-		kho_release_scratch();
 
 		if (kho_mem_retrieve(kho_get_fdt()))
 			kho_in.fdt_phys = 0;
diff --git a/mm/memblock.c b/mm/memblock.c
index a6a1c91e276d..01a962681726 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -1026,40 +1026,6 @@ int __init_memblock memblock_physmem_add(phys_addr_t base, phys_addr_t size)
 }
 #endif
 
-#ifdef CONFIG_MEMBLOCK_KHO_SCRATCH
-__init void memblock_set_kho_scratch_only(void)
-{
-	kho_scratch_only = true;
-}
-
-__init void memblock_clear_kho_scratch_only(void)
-{
-	kho_scratch_only = false;
-}
-
-__init void memmap_init_kho_scratch_pages(void)
-{
-	phys_addr_t start, end;
-	unsigned long pfn;
-	int nid;
-	u64 i;
-
-	if (!IS_ENABLED(CONFIG_DEFERRED_STRUCT_PAGE_INIT))
-		return;
-
-	/*
-	 * Initialize struct pages for free scratch memory.
-	 * The struct pages for reserved scratch memory will be set up in
-	 * memmap_init_reserved_pages()
-	 */
-	__for_each_mem_range(i, &memblock.memory, NULL, NUMA_NO_NODE,
-			     MEMBLOCK_KHO_SCRATCH, &start, &end, &nid) {
-		for (pfn = PFN_UP(start); pfn < PFN_DOWN(end); pfn++)
-			init_deferred_page(pfn, nid);
-	}
-}
-#endif
-
 /**
  * memblock_setclr_flag - set or clear flag for a memory region
  * @type: memblock type to set/clear flag for
@@ -2533,6 +2499,28 @@ int reserve_mem_release_by_name(const char *name)
 	return 1;
 }
 
+#ifdef CONFIG_MEMBLOCK_KHO_SCRATCH
+__init void memblock_set_kho_scratch_only(void)
+{
+	kho_scratch_only = true;
+}
+
+__init void memblock_clear_kho_scratch_only(void)
+{
+	kho_scratch_only = false;
+}
+
+bool __init_memblock memblock_is_kho_scratch_memory(phys_addr_t addr)
+{
+	int i = memblock_search(&memblock.memory, addr);
+
+	if (i == -1)
+		return false;
+
+	return memblock_is_kho_scratch(&memblock.memory.regions[i]);
+}
+#endif
+
 #ifdef CONFIG_KEXEC_HANDOVER
 
 static int __init reserved_mem_preserve(void)
diff --git a/mm/mm_init.c b/mm/mm_init.c
index f9f8e1af921c..eddc0f03a779 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -692,9 +692,11 @@ void __meminit __init_page_from_nid(unsigned long pfn, int nid)
 	}
 	__init_single_page(pfn_to_page(pfn), pfn, zid, nid);
 
-	if (pageblock_aligned(pfn))
-		init_pageblock_migratetype(pfn_to_page(pfn), MIGRATE_MOVABLE,
-				false);
+	if (pageblock_aligned(pfn)) {
+		enum migratetype mt =
+			kho_scratch_migratetype(pfn, MIGRATE_MOVABLE);
+		init_pageblock_migratetype(pfn_to_page(pfn), mt, false);
+	}
 }
 
 #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
@@ -927,7 +929,8 @@ void __meminit memmap_init_range(unsigned long size, int nid, unsigned long zone
 static void __init memmap_init_zone_range(struct zone *zone,
 					  unsigned long start_pfn,
 					  unsigned long end_pfn,
-					  unsigned long *hole_pfn)
+					  unsigned long *hole_pfn,
+					  enum migratetype mt)
 {
 	unsigned long zone_start_pfn = zone->zone_start_pfn;
 	unsigned long zone_end_pfn = zone_start_pfn + zone->spanned_pages;
@@ -940,8 +943,7 @@ static void __init memmap_init_zone_range(struct zone *zone,
 		return;
 
 	memmap_init_range(end_pfn - start_pfn, nid, zone_id, start_pfn,
-			  zone_end_pfn, MEMINIT_EARLY, NULL, MIGRATE_MOVABLE,
-			  false);
+			  zone_end_pfn, MEMINIT_EARLY, NULL, mt, false);
 
 	if (*hole_pfn < start_pfn)
 		init_unavailable_range(*hole_pfn, start_pfn, zone_id, nid);
@@ -957,6 +959,8 @@ 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);
+		enum migratetype mt =
+			kho_scratch_migratetype(start_pfn, MIGRATE_MOVABLE);
 
 		for (j = 0; j < MAX_NR_ZONES; j++) {
 			struct zone *zone = node->node_zones + j;
@@ -965,7 +969,7 @@ static void __init memmap_init(void)
 				continue;
 
 			memmap_init_zone_range(zone, start_pfn, end_pfn,
-					       &hole_pfn);
+					       &hole_pfn, mt);
 			zone_id = j;
 		}
 	}
@@ -1970,7 +1974,7 @@ unsigned long __init node_map_pfn_alignment(void)
 
 #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
 static void __init deferred_free_pages(unsigned long pfn,
-		unsigned long nr_pages)
+		unsigned long nr_pages, enum migratetype mt)
 {
 	struct page *page;
 	unsigned long i;
@@ -1983,8 +1987,7 @@ static void __init deferred_free_pages(unsigned long pfn,
 	/* Free a large naturally-aligned chunk if possible */
 	if (nr_pages == MAX_ORDER_NR_PAGES && IS_MAX_ORDER_ALIGNED(pfn)) {
 		for (i = 0; i < nr_pages; i += pageblock_nr_pages)
-			init_pageblock_migratetype(page + i, MIGRATE_MOVABLE,
-					false);
+			init_pageblock_migratetype(page + i, mt, false);
 		__free_pages_core(page, MAX_PAGE_ORDER, MEMINIT_EARLY);
 		return;
 	}
@@ -1994,8 +1997,7 @@ static void __init deferred_free_pages(unsigned long pfn,
 
 	for (i = 0; i < nr_pages; i++, page++, pfn++) {
 		if (pageblock_aligned(pfn))
-			init_pageblock_migratetype(page, MIGRATE_MOVABLE,
-					false);
+			init_pageblock_migratetype(page, mt, false);
 		__free_pages_core(page, 0, MEMINIT_EARLY);
 	}
 }
@@ -2053,6 +2055,8 @@ deferred_init_memmap_chunk(unsigned long start_pfn, unsigned long end_pfn,
 	for_each_free_mem_range(i, nid, 0, &start, &end, NULL) {
 		unsigned long spfn = PFN_UP(start);
 		unsigned long epfn = PFN_DOWN(end);
+		enum migratetype mt =
+			kho_scratch_migratetype(spfn, MIGRATE_MOVABLE);
 
 		if (spfn >= end_pfn)
 			break;
@@ -2065,7 +2069,7 @@ deferred_init_memmap_chunk(unsigned long start_pfn, unsigned long end_pfn,
 			unsigned long chunk_end = min(mo_pfn, epfn);
 
 			nr_pages += deferred_init_pages(zone, spfn, chunk_end);
-			deferred_free_pages(spfn, chunk_end - spfn);
+			deferred_free_pages(spfn, chunk_end - spfn, mt);
 
 			spfn = chunk_end;
 
-- 
2.54.0.rc2.533.g4f5dca5207-goog

Re: [PATCH v9 1/3] kho: fix deferred initialization of scratch areas

[Pratyush Yadav]

On Thu, Apr 23 2026, Michal Clapinski wrote:

> Currently, if CONFIG_DEFERRED_STRUCT_PAGE_INIT is enabled,
> kho_release_scratch() will initialize the struct pages and set migratetype
> of KHO scratch. Unless the whole scratch fits below first_deferred_pfn,
> some of that will be overwritten either by deferred_init_pages() or
> memmap_init_reserved_range().
>
> To fix it, make memmap_init_range(), deferred_init_memmap_chunk() and
> __init_page_from_nid() recognize KHO scratch regions and set
> migratetype of pageblocks in those regions to MIGRATE_CMA.
>
> Co-developed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> Signed-off-by: Michal Clapinski <mclapinski@google.com>

Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>

[...]

-- 
Regards,
Pratyush Yadav

Re: [PATCH v9 1/3] kho: fix deferred initialization of scratch areas

[Pasha Tatashin]

On 04-23 14:25, Michal Clapinski wrote:
> Currently, if CONFIG_DEFERRED_STRUCT_PAGE_INIT is enabled,
> kho_release_scratch() will initialize the struct pages and set migratetype
> of KHO scratch. Unless the whole scratch fits below first_deferred_pfn,
> some of that will be overwritten either by deferred_init_pages() or
> memmap_init_reserved_range().
> 
> To fix it, make memmap_init_range(), deferred_init_memmap_chunk() and
> __init_page_from_nid() recognize KHO scratch regions and set
> migratetype of pageblocks in those regions to MIGRATE_CMA.
> 
> Co-developed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> Signed-off-by: Michal Clapinski <mclapinski@google.com>

Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com> 

Re: [PATCH v9 1/3] kho: fix deferred initialization of scratch areas

[Mike Rapoport]

On Thu, Apr 23, 2026 at 02:25:36PM +0200, Michal Clapinski wrote:
> Currently, if CONFIG_DEFERRED_STRUCT_PAGE_INIT is enabled,
> kho_release_scratch() will initialize the struct pages and set migratetype
> of KHO scratch. Unless the whole scratch fits below first_deferred_pfn,
> some of that will be overwritten either by deferred_init_pages() or
> memmap_init_reserved_range().
> 
> To fix it, make memmap_init_range(), deferred_init_memmap_chunk() and
> __init_page_from_nid() recognize KHO scratch regions and set
> migratetype of pageblocks in those regions to MIGRATE_CMA.
> 
> Co-developed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> Signed-off-by: Michal Clapinski <mclapinski@google.com>

Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>

> ---
>  include/linux/memblock.h           | 21 +++++++++--
>  kernel/liveupdate/kexec_handover.c | 25 -------------
>  mm/memblock.c                      | 56 ++++++++++++------------------
>  mm/mm_init.c                       | 30 +++++++++-------
>  4 files changed, 58 insertions(+), 74 deletions(-)
> 
> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> index b0f750d22a7b..5afcd99aa8c1 100644
> --- a/include/linux/memblock.h
> +++ b/include/linux/memblock.h
> @@ -613,11 +613,28 @@ static inline void memtest_report_meminfo(struct seq_file *m) { }
>  #ifdef CONFIG_MEMBLOCK_KHO_SCRATCH
>  void memblock_set_kho_scratch_only(void);
>  void memblock_clear_kho_scratch_only(void);
> -void memmap_init_kho_scratch_pages(void);
> +bool memblock_is_kho_scratch_memory(phys_addr_t addr);
> +
> +static inline enum migratetype kho_scratch_migratetype(unsigned long pfn,
> +						       enum migratetype mt)
> +{
> +	if (memblock_is_kho_scratch_memory(PFN_PHYS(pfn)))
> +		return MIGRATE_CMA;
> +	return mt;
> +}
>  #else
>  static inline void memblock_set_kho_scratch_only(void) { }
>  static inline void memblock_clear_kho_scratch_only(void) { }
> -static inline void memmap_init_kho_scratch_pages(void) {}
> +static inline bool memblock_is_kho_scratch_memory(phys_addr_t addr)
> +{
> +	return false;
> +}
> +
> +static inline enum migratetype kho_scratch_migratetype(unsigned long pfn,
> +						       enum migratetype mt)
> +{
> +	return mt;
> +}
>  #endif
>  
>  #endif /* _LINUX_MEMBLOCK_H */
> diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c
> index 18509d8082ea..a507366a2cf9 100644
> --- a/kernel/liveupdate/kexec_handover.c
> +++ b/kernel/liveupdate/kexec_handover.c
> @@ -1576,35 +1576,10 @@ static __init int kho_init(void)
>  }
>  fs_initcall(kho_init);
>  
> -static void __init kho_release_scratch(void)
> -{
> -	phys_addr_t start, end;
> -	u64 i;
> -
> -	memmap_init_kho_scratch_pages();
> -
> -	/*
> -	 * Mark scratch mem as CMA before we return it. That way we
> -	 * ensure that no kernel allocations happen on it. That means
> -	 * we can reuse it as scratch memory again later.
> -	 */
> -	__for_each_mem_range(i, &memblock.memory, NULL, NUMA_NO_NODE,
> -			     MEMBLOCK_KHO_SCRATCH, &start, &end, NULL) {
> -		ulong start_pfn = pageblock_start_pfn(PFN_DOWN(start));
> -		ulong end_pfn = pageblock_align(PFN_UP(end));
> -		ulong pfn;
> -
> -		for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages)
> -			init_pageblock_migratetype(pfn_to_page(pfn),
> -						   MIGRATE_CMA, false);
> -	}
> -}
> -
>  void __init kho_memory_init(void)
>  {
>  	if (kho_in.scratch_phys) {
>  		kho_scratch = phys_to_virt(kho_in.scratch_phys);
> -		kho_release_scratch();
>  
>  		if (kho_mem_retrieve(kho_get_fdt()))
>  			kho_in.fdt_phys = 0;
> diff --git a/mm/memblock.c b/mm/memblock.c
> index a6a1c91e276d..01a962681726 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -1026,40 +1026,6 @@ int __init_memblock memblock_physmem_add(phys_addr_t base, phys_addr_t size)
>  }
>  #endif
>  
> -#ifdef CONFIG_MEMBLOCK_KHO_SCRATCH
> -__init void memblock_set_kho_scratch_only(void)
> -{
> -	kho_scratch_only = true;
> -}
> -
> -__init void memblock_clear_kho_scratch_only(void)
> -{
> -	kho_scratch_only = false;
> -}
> -
> -__init void memmap_init_kho_scratch_pages(void)
> -{
> -	phys_addr_t start, end;
> -	unsigned long pfn;
> -	int nid;
> -	u64 i;
> -
> -	if (!IS_ENABLED(CONFIG_DEFERRED_STRUCT_PAGE_INIT))
> -		return;
> -
> -	/*
> -	 * Initialize struct pages for free scratch memory.
> -	 * The struct pages for reserved scratch memory will be set up in
> -	 * memmap_init_reserved_pages()
> -	 */
> -	__for_each_mem_range(i, &memblock.memory, NULL, NUMA_NO_NODE,
> -			     MEMBLOCK_KHO_SCRATCH, &start, &end, &nid) {
> -		for (pfn = PFN_UP(start); pfn < PFN_DOWN(end); pfn++)
> -			init_deferred_page(pfn, nid);
> -	}
> -}
> -#endif
> -
>  /**
>   * memblock_setclr_flag - set or clear flag for a memory region
>   * @type: memblock type to set/clear flag for
> @@ -2533,6 +2499,28 @@ int reserve_mem_release_by_name(const char *name)
>  	return 1;
>  }
>  
> +#ifdef CONFIG_MEMBLOCK_KHO_SCRATCH
> +__init void memblock_set_kho_scratch_only(void)
> +{
> +	kho_scratch_only = true;
> +}
> +
> +__init void memblock_clear_kho_scratch_only(void)
> +{
> +	kho_scratch_only = false;
> +}
> +
> +bool __init_memblock memblock_is_kho_scratch_memory(phys_addr_t addr)
> +{
> +	int i = memblock_search(&memblock.memory, addr);
> +
> +	if (i == -1)
> +		return false;
> +
> +	return memblock_is_kho_scratch(&memblock.memory.regions[i]);
> +}
> +#endif
> +
>  #ifdef CONFIG_KEXEC_HANDOVER
>  
>  static int __init reserved_mem_preserve(void)
> diff --git a/mm/mm_init.c b/mm/mm_init.c
> index f9f8e1af921c..eddc0f03a779 100644
> --- a/mm/mm_init.c
> +++ b/mm/mm_init.c
> @@ -692,9 +692,11 @@ void __meminit __init_page_from_nid(unsigned long pfn, int nid)
>  	}
>  	__init_single_page(pfn_to_page(pfn), pfn, zid, nid);
>  
> -	if (pageblock_aligned(pfn))
> -		init_pageblock_migratetype(pfn_to_page(pfn), MIGRATE_MOVABLE,
> -				false);
> +	if (pageblock_aligned(pfn)) {
> +		enum migratetype mt =
> +			kho_scratch_migratetype(pfn, MIGRATE_MOVABLE);
> +		init_pageblock_migratetype(pfn_to_page(pfn), mt, false);
> +	}
>  }
>  
>  #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
> @@ -927,7 +929,8 @@ void __meminit memmap_init_range(unsigned long size, int nid, unsigned long zone
>  static void __init memmap_init_zone_range(struct zone *zone,
>  					  unsigned long start_pfn,
>  					  unsigned long end_pfn,
> -					  unsigned long *hole_pfn)
> +					  unsigned long *hole_pfn,
> +					  enum migratetype mt)
>  {
>  	unsigned long zone_start_pfn = zone->zone_start_pfn;
>  	unsigned long zone_end_pfn = zone_start_pfn + zone->spanned_pages;
> @@ -940,8 +943,7 @@ static void __init memmap_init_zone_range(struct zone *zone,
>  		return;
>  
>  	memmap_init_range(end_pfn - start_pfn, nid, zone_id, start_pfn,
> -			  zone_end_pfn, MEMINIT_EARLY, NULL, MIGRATE_MOVABLE,
> -			  false);
> +			  zone_end_pfn, MEMINIT_EARLY, NULL, mt, false);
>  
>  	if (*hole_pfn < start_pfn)
>  		init_unavailable_range(*hole_pfn, start_pfn, zone_id, nid);
> @@ -957,6 +959,8 @@ 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);
> +		enum migratetype mt =
> +			kho_scratch_migratetype(start_pfn, MIGRATE_MOVABLE);
>  
>  		for (j = 0; j < MAX_NR_ZONES; j++) {
>  			struct zone *zone = node->node_zones + j;
> @@ -965,7 +969,7 @@ static void __init memmap_init(void)
>  				continue;
>  
>  			memmap_init_zone_range(zone, start_pfn, end_pfn,
> -					       &hole_pfn);
> +					       &hole_pfn, mt);
>  			zone_id = j;
>  		}
>  	}
> @@ -1970,7 +1974,7 @@ unsigned long __init node_map_pfn_alignment(void)
>  
>  #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
>  static void __init deferred_free_pages(unsigned long pfn,
> -		unsigned long nr_pages)
> +		unsigned long nr_pages, enum migratetype mt)
>  {
>  	struct page *page;
>  	unsigned long i;
> @@ -1983,8 +1987,7 @@ static void __init deferred_free_pages(unsigned long pfn,
>  	/* Free a large naturally-aligned chunk if possible */
>  	if (nr_pages == MAX_ORDER_NR_PAGES && IS_MAX_ORDER_ALIGNED(pfn)) {
>  		for (i = 0; i < nr_pages; i += pageblock_nr_pages)
> -			init_pageblock_migratetype(page + i, MIGRATE_MOVABLE,
> -					false);
> +			init_pageblock_migratetype(page + i, mt, false);
>  		__free_pages_core(page, MAX_PAGE_ORDER, MEMINIT_EARLY);
>  		return;
>  	}
> @@ -1994,8 +1997,7 @@ static void __init deferred_free_pages(unsigned long pfn,
>  
>  	for (i = 0; i < nr_pages; i++, page++, pfn++) {
>  		if (pageblock_aligned(pfn))
> -			init_pageblock_migratetype(page, MIGRATE_MOVABLE,
> -					false);
> +			init_pageblock_migratetype(page, mt, false);
>  		__free_pages_core(page, 0, MEMINIT_EARLY);
>  	}
>  }
> @@ -2053,6 +2055,8 @@ deferred_init_memmap_chunk(unsigned long start_pfn, unsigned long end_pfn,
>  	for_each_free_mem_range(i, nid, 0, &start, &end, NULL) {
>  		unsigned long spfn = PFN_UP(start);
>  		unsigned long epfn = PFN_DOWN(end);
> +		enum migratetype mt =
> +			kho_scratch_migratetype(spfn, MIGRATE_MOVABLE);
>  
>  		if (spfn >= end_pfn)
>  			break;
> @@ -2065,7 +2069,7 @@ deferred_init_memmap_chunk(unsigned long start_pfn, unsigned long end_pfn,
>  			unsigned long chunk_end = min(mo_pfn, epfn);
>  
>  			nr_pages += deferred_init_pages(zone, spfn, chunk_end);
> -			deferred_free_pages(spfn, chunk_end - spfn);
> +			deferred_free_pages(spfn, chunk_end - spfn, mt);
>  
>  			spfn = chunk_end;
>  
> -- 
> 2.54.0.rc2.533.g4f5dca5207-goog
> 

-- 
Sincerely yours,
Mike.

[PATCH v9 2/3] kho: make preserved pages compatible with deferred struct page init

[Michal Clapinski]

From: Evangelos Petrongonas <epetron@amazon.de>

When CONFIG_DEFERRED_STRUCT_PAGE_INIT is enabled, struct page
initialization is deferred to parallel kthreads that run later
in the boot process.

During KHO restoration, kho_preserved_memory_reserve() writes metadata
for each preserved memory region. However, if the struct page has not
been initialized, this write targets uninitialized memory, potentially
leading to errors like:
BUG: unable to handle page fault for address: ...

Fix this by introducing kho_get_preserved_page(),  which ensures
all struct pages in a preserved region are initialized by calling
init_deferred_page() which is a no-op when the struct page is already
initialized.

Signed-off-by: Evangelos Petrongonas <epetron@amazon.de>
Co-developed-by: Michal Clapinski <mclapinski@google.com>
Signed-off-by: Michal Clapinski <mclapinski@google.com>
Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
---
 kernel/liveupdate/Kconfig          |  2 --
 kernel/liveupdate/kexec_handover.c | 27 ++++++++++++++++++++++++++-
 2 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/kernel/liveupdate/Kconfig b/kernel/liveupdate/Kconfig
index 1a8513f16ef7..c13af38ba23a 100644
--- a/kernel/liveupdate/Kconfig
+++ b/kernel/liveupdate/Kconfig
@@ -1,12 +1,10 @@
 # SPDX-License-Identifier: GPL-2.0-only
 
 menu "Live Update and Kexec HandOver"
-	depends on !DEFERRED_STRUCT_PAGE_INIT
 
 config KEXEC_HANDOVER
 	bool "kexec handover"
 	depends on ARCH_SUPPORTS_KEXEC_HANDOVER && ARCH_SUPPORTS_KEXEC_FILE
-	depends on !DEFERRED_STRUCT_PAGE_INIT
 	select MEMBLOCK_KHO_SCRATCH
 	select KEXEC_FILE
 	select LIBFDT
diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c
index a507366a2cf9..d5718bef6d4d 100644
--- a/kernel/liveupdate/kexec_handover.c
+++ b/kernel/liveupdate/kexec_handover.c
@@ -473,6 +473,31 @@ struct page *kho_restore_pages(phys_addr_t phys, unsigned long nr_pages)
 }
 EXPORT_SYMBOL_GPL(kho_restore_pages);
 
+/*
+ * With CONFIG_DEFERRED_STRUCT_PAGE_INIT, struct pages in higher memory regions
+ * may not be initialized yet at the time KHO deserializes preserved memory.
+ * KHO uses the struct page to store metadata and a later initialization would
+ * overwrite it.
+ * Ensure all the struct pages in the preservation are
+ * initialized. kho_preserved_memory_reserve() marks the reservation as noinit
+ * to make sure they don't get re-initialized later.
+ */
+static struct page *__init kho_get_preserved_page(phys_addr_t phys,
+						  unsigned int order)
+{
+	unsigned long pfn = PHYS_PFN(phys);
+	int nid;
+
+	if (!IS_ENABLED(CONFIG_DEFERRED_STRUCT_PAGE_INIT))
+		return pfn_to_page(pfn);
+
+	nid = early_pfn_to_nid(pfn);
+	for (unsigned long i = 0; i < (1UL << order); i++)
+		init_deferred_page(pfn + i, nid);
+
+	return pfn_to_page(pfn);
+}
+
 static int __init kho_preserved_memory_reserve(phys_addr_t phys,
 					       unsigned int order)
 {
@@ -481,7 +506,7 @@ static int __init kho_preserved_memory_reserve(phys_addr_t phys,
 	u64 sz;
 
 	sz = 1 << (order + PAGE_SHIFT);
-	page = phys_to_page(phys);
+	page = kho_get_preserved_page(phys, order);
 
 	/* Reserve the memory preserved in KHO in memblock */
 	memblock_reserve(phys, sz);
-- 
2.54.0.rc2.533.g4f5dca5207-goog

[PATCH v9 3/3] selftests: kho: test with deferred struct page init

[Michal Clapinski]

Enable DEFERRED_STRUCT_PAGE_INIT which depends on SMP.
Also enable additional debugging options.

Signed-off-by: Michal Clapinski <mclapinski@google.com>
---
 tools/testing/selftests/kho/vmtest.sh | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tools/testing/selftests/kho/vmtest.sh b/tools/testing/selftests/kho/vmtest.sh
index 49fdac8e8b15..0014bd76e88d 100755
--- a/tools/testing/selftests/kho/vmtest.sh
+++ b/tools/testing/selftests/kho/vmtest.sh
@@ -59,10 +59,14 @@ function build_kernel() {
 	tee "$kconfig" > "$kho_config" <<EOF
 CONFIG_BLK_DEV_INITRD=y
 CONFIG_KEXEC_HANDOVER=y
+CONFIG_KEXEC_HANDOVER_DEBUG=y
 CONFIG_KEXEC_HANDOVER_DEBUGFS=y
 CONFIG_TEST_KEXEC_HANDOVER=y
 CONFIG_DEBUG_KERNEL=y
 CONFIG_DEBUG_VM=y
+CONFIG_DEBUG_VM_PGFLAGS=y
+CONFIG_SMP=y
+CONFIG_DEFERRED_STRUCT_PAGE_INIT=y
 $arch_kconfig
 EOF
 
-- 
2.54.0.rc2.533.g4f5dca5207-goog

Re: [PATCH v9 3/3] selftests: kho: test with deferred struct page init

[Pratyush Yadav]

On Thu, Apr 23 2026, Michal Clapinski wrote:

> Enable DEFERRED_STRUCT_PAGE_INIT which depends on SMP.
> Also enable additional debugging options.
>
> Signed-off-by: Michal Clapinski <mclapinski@google.com>

Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>

[...]

-- 
Regards,
Pratyush Yadav

Re: [PATCH v9 3/3] selftests: kho: test with deferred struct page init

[Pasha Tatashin]

On 04-23 14:25, Michal Clapinski wrote:
> Enable DEFERRED_STRUCT_PAGE_INIT which depends on SMP.
> Also enable additional debugging options.
> 
> Signed-off-by: Michal Clapinski <mclapinski@google.com>

Acked-by: Pasha Tatashin <pasha.tatashin@soleen.com> 

> ---
>  tools/testing/selftests/kho/vmtest.sh | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/tools/testing/selftests/kho/vmtest.sh b/tools/testing/selftests/kho/vmtest.sh
> index 49fdac8e8b15..0014bd76e88d 100755
> --- a/tools/testing/selftests/kho/vmtest.sh
> +++ b/tools/testing/selftests/kho/vmtest.sh
> @@ -59,10 +59,14 @@ function build_kernel() {
>  	tee "$kconfig" > "$kho_config" <<EOF
>  CONFIG_BLK_DEV_INITRD=y
>  CONFIG_KEXEC_HANDOVER=y
> +CONFIG_KEXEC_HANDOVER_DEBUG=y
>  CONFIG_KEXEC_HANDOVER_DEBUGFS=y
>  CONFIG_TEST_KEXEC_HANDOVER=y
>  CONFIG_DEBUG_KERNEL=y
>  CONFIG_DEBUG_VM=y
> +CONFIG_DEBUG_VM_PGFLAGS=y
> +CONFIG_SMP=y
> +CONFIG_DEFERRED_STRUCT_PAGE_INIT=y
>  $arch_kconfig
>  EOF
>  
> -- 
> 2.54.0.rc2.533.g4f5dca5207-goog
> 

Re: [PATCH v9 3/3] selftests: kho: test with deferred struct page init

[Mike Rapoport]

On Thu, Apr 23, 2026 at 02:25:38PM +0200, Michal Clapinski wrote:
> Enable DEFERRED_STRUCT_PAGE_INIT which depends on SMP.
> Also enable additional debugging options.
> 
> Signed-off-by: Michal Clapinski <mclapinski@google.com>

Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>

> ---
>  tools/testing/selftests/kho/vmtest.sh | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/tools/testing/selftests/kho/vmtest.sh b/tools/testing/selftests/kho/vmtest.sh
> index 49fdac8e8b15..0014bd76e88d 100755
> --- a/tools/testing/selftests/kho/vmtest.sh
> +++ b/tools/testing/selftests/kho/vmtest.sh
> @@ -59,10 +59,14 @@ function build_kernel() {
>  	tee "$kconfig" > "$kho_config" <<EOF
>  CONFIG_BLK_DEV_INITRD=y
>  CONFIG_KEXEC_HANDOVER=y
> +CONFIG_KEXEC_HANDOVER_DEBUG=y
>  CONFIG_KEXEC_HANDOVER_DEBUGFS=y
>  CONFIG_TEST_KEXEC_HANDOVER=y
>  CONFIG_DEBUG_KERNEL=y
>  CONFIG_DEBUG_VM=y
> +CONFIG_DEBUG_VM_PGFLAGS=y
> +CONFIG_SMP=y
> +CONFIG_DEFERRED_STRUCT_PAGE_INIT=y
>  $arch_kconfig
>  EOF
>  
> -- 
> 2.54.0.rc2.533.g4f5dca5207-goog
> 

-- 
Sincerely yours,
Mike.