memblock: introduce memmap_init_kho_scratch()

With deferred initialization of struct page it will be necessary to
initialize memory map for KHO scratch regions early.

Add memmap_init_kho_scratch() method that will allow such initialization
in upcoming patches.

Link: https://lkml.kernel.org/r/20250509074635.3187114-4-changyuanl@google.com
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Changyuan Lyu <changyuanl@google.com>
Cc: Alexander Graf <graf@amazon.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Anthony Yznaga <anthony.yznaga@oracle.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Ben Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Gowans <jgowans@amazon.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Pratyush Yadav <ptyadav@amazon.de>
Cc: Rob Herring <robh@kernel.org>
Cc: Saravana Kannan <saravanak@google.com>
Cc: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Thomas Lendacky <thomas.lendacky@amd.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

4 files changed, 34 insertions, 3 deletions

diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index 993937a6b962..bb19a2534224 100644
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h
@@ -635,9 +635,11 @@ 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);
 #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) {}
 #endif
 
 #endif /* _LINUX_MEMBLOCK_H */
diff --git a/mm/internal.h b/mm/internal.h
index 780481a8be0e..cf7c0e9ef7ec 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -1119,6 +1119,8 @@ DECLARE_STATIC_KEY_TRUE(deferred_pages);
 bool __init deferred_grow_zone(struct zone *zone, unsigned int order);
 #endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */
 
+void init_deferred_page(unsigned long pfn, int nid);
+
 enum mminit_level {
 	MMINIT_WARNING,
 	MMINIT_VERIFY,
diff --git a/mm/memblock.c b/mm/memblock.c
index 58cb82d444b1..ec30d850e195 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -953,6 +953,28 @@ __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
+	 * reserve_bootmem_region()
+	 */
+	__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
 
 /**
diff --git a/mm/mm_init.c b/mm/mm_init.c
index c275ae561b6f..62d7f551b295 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -743,7 +743,7 @@ defer_init(int nid, unsigned long pfn, unsigned long end_pfn)
 	return false;
 }
 
-static void __meminit init_deferred_page(unsigned long pfn, int nid)
+static void __meminit __init_deferred_page(unsigned long pfn, int nid)
 {
 	if (early_page_initialised(pfn, nid))
 		return;
@@ -763,11 +763,16 @@ static inline bool defer_init(int nid, unsigned long pfn, unsigned long end_pfn)
 	return false;
 }
 
-static inline void init_deferred_page(unsigned long pfn, int nid)
+static inline void __init_deferred_page(unsigned long pfn, int nid)
 {
 }
 #endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */
 
+void __meminit init_deferred_page(unsigned long pfn, int nid)
+{
+	__init_deferred_page(pfn, nid);
+}
+
 /*
  * Initialised pages do not have PageReserved set. This function is
  * called for each range allocated by the bootmem allocator and
@@ -784,7 +789,7 @@ void __meminit reserve_bootmem_region(phys_addr_t start,
 		if (pfn_valid(start_pfn)) {
 			struct page *page = pfn_to_page(start_pfn);
 
-			init_deferred_page(start_pfn, nid);
+			__init_deferred_page(start_pfn, nid);
 
 			/*
 			 * no need for atomic set_bit because the struct