From: Mike Rapoport <redacted>

The arm64's version of pfn_valid() differs from the generic because of two
reasons:

* Parts of the memory map are freed during boot. This makes it necessary to
  verify that there is actual physical memory that corresponds to a pfn
  which is done by querying memblock.

* There are NOMAP memory regions. These regions are not mapped in the
  linear map and until the previous commit the struct pages representing
  these areas had default values.

As the consequence of absence of the special treatment of NOMAP regions in
the memory map it was necessary to use memblock_is_map_memory() in
pfn_valid() and to have pfn_valid_within() aliased to pfn_valid() so that
generic mm functionality would not treat a NOMAP page as a normal page.

Since the NOMAP regions are now marked as PageReserved(), pfn walkers and
the rest of core mm will treat them as unusable memory and thus
pfn_valid_within() is no longer required at all and can be disabled by
removing CONFIG_HOLES_IN_ZONE on arm64.

pfn_valid() can be slightly simplified by replacing
memblock_is_map_memory() with memblock_is_memory().

...

--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig

@@ -1052,9 +1052,6 @@ config NEED_PER_CPU_EMBED_FIRST_CHUNK
 	def_bool y
 	depends on NUMA
 
-config HOLES_IN_ZONE
-	def_bool y
-
 source "kernel/Kconfig.hz"
 
 config ARCH_SPARSEMEM_ENABLE

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 798f74f501d5..fb07218da2c0 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c

@@ -251,7 +251,7 @@ int pfn_valid(unsigned long pfn)
 	if (!early_section(ms))
 		return pfn_section_valid(ms, pfn);
 
-	return memblock_is_map_memory(addr);
+	return memblock_is_memory(addr);
 }
 EXPORT_SYMBOL(pfn_valid);