From: Mike Rapoport <redacted>

The struct pages representing a reserved memory region are initialized
using reserve_bootmem_range() function. This function is called for each
reserved region just before the memory is freed from memblock to the buddy
page allocator.

The struct pages for MEMBLOCK_NOMAP regions are kept with the default
values set by the memory map initialization which makes it necessary to
have a special treatment for such pages in pfn_valid() and
pfn_valid_within().

Split out initialization of the reserved pages to a function with a
meaningful name and treat the MEMBLOCK_NOMAP regions the same way as the
reserved regions and mark struct pages for the NOMAP regions as
PageReserved.

Signed-off-by: Mike Rapoport <redacted>
---
  include/linux/memblock.h |  4 +++-
  mm/memblock.c            | 28 ++++++++++++++++++++++++++--
  2 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index 5984fff3f175..634c1a578db8 100644
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h

@@ -30,7 +30,9 @@ extern unsigned long long max_possible_pfn;
   * @MEMBLOCK_NONE: no special request
   * @MEMBLOCK_HOTPLUG: hotpluggable region
   * @MEMBLOCK_MIRROR: mirrored region
- * @MEMBLOCK_NOMAP: don't add to kernel direct mapping
+ * @MEMBLOCK_NOMAP: don't add to kernel direct mapping and treat as
+ * reserved in the memory map; refer to memblock_mark_nomap() description
+ * for futher details
   */
  enum memblock_flags {
  	MEMBLOCK_NONE		= 0x0,	/* No special request */

diff --git a/mm/memblock.c b/mm/memblock.c
index afaefa8fc6ab..3abf2c3fea7f 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c

@@ -906,6 +906,11 @@ int __init_memblock memblock_mark_mirror(phys_addr_t base, phys_addr_t size)
   * @base: the base phys addr of the region
   * @size: the size of the region
   *
+ * The memory regions marked with %MEMBLOCK_NOMAP will not be added to the
+ * direct mapping of the physical memory. These regions will still be
+ * covered by the memory map. The struct page representing NOMAP memory
+ * frames in the memory map will be PageReserved()
+ *
   * Return: 0 on success, -errno on failure.
   */
  int __init_memblock memblock_mark_nomap(phys_addr_t base, phys_addr_t size)

@@ -2002,6 +2007,26 @@ static unsigned long __init __free_memory_core(phys_addr_t start,
  	return end_pfn - start_pfn;
  }
  
+static void __init memmap_init_reserved_pages(void)
+{
+	struct memblock_region *region;
+	phys_addr_t start, end;
+	u64 i;
+
+	/* initialize struct pages for the reserved regions */
+	for_each_reserved_mem_range(i, &start, &end)
+		reserve_bootmem_region(start, end);
+
+	/* and also treat struct pages for the NOMAP regions as PageReserved */
+	for_each_mem_region(region) {
+		if (memblock_is_nomap(region)) {
+			start = region->base;
+			end = start + region->size;
+			reserve_bootmem_region(start, end);
+		}
+	}
+}
+
  static unsigned long __init free_low_memory_core_early(void)
  {
  	unsigned long count = 0;

@@ -2010,8 +2035,7 @@ static unsigned long __init free_low_memory_core_early(void)
  
  	memblock_clear_hotplug(0, -1);
  
-	for_each_reserved_mem_range(i, &start, &end)
-		reserve_bootmem_region(start, end);
+	memmap_init_reserved_pages();
  
  	/*
  	 * We need to use NUMA_NO_NODE instead of NODE_DATA(0)->node_id