arm64: Kconfig: Remove ARCH_HAS_HOLES_MEMORYMODEL

include/linux/mmzone.h describes ARCH_HAS_HOLES_MEMORYMODEL as
relevant when parts the memmap have been free()d. This would
happen on systems where memory is smaller than a sparsemem-section,
and the extra struct pages are expensive. pfn_valid() on these
systems returns true for the whole sparsemem-section, so an extra
memmap_valid_within() check is needed.

On arm64 we have nomap memory, so always provide pfn_valid() to test
for nomap pages. This means ARCH_HAS_HOLES_MEMORYMODEL's extra checks
are already rolled up into pfn_valid().

Remove it.
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/Kconfig

@@ -771,9 +771,6 @@ source kernel/Kconfig.hz
 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
 	def_bool y
 
-config ARCH_HAS_HOLES_MEMORYMODEL
-	def_bool y if SPARSEMEM
-
 config ARCH_SPARSEMEM_ENABLE
 	def_bool y
 	select SPARSEMEM_VMEMMAP_ENABLE
@@ -788,7 +785,7 @@ config ARCH_FLATMEM_ENABLE
 	def_bool !NUMA
 
 config HAVE_ARCH_PFN_VALID
-	def_bool ARCH_HAS_HOLES_MEMORYMODEL || !SPARSEMEM
+	def_bool y
 
 config HW_PERF_EVENTS
 	def_bool y

arch/arm64/include/asm/page.h

@@ -37,9 +37,7 @@ extern void clear_page(void *to);
 
 typedef struct page *pgtable_t;
 
-#ifdef CONFIG_HAVE_ARCH_PFN_VALID
 extern int pfn_valid(unsigned long);
-#endif
 
 #include <asm/memory.h>
 

arch/arm64/mm/init.c

@@ -284,7 +284,6 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max)
 
 #endif /* CONFIG_NUMA */
 
-#ifdef CONFIG_HAVE_ARCH_PFN_VALID
 int pfn_valid(unsigned long pfn)
 {
 	phys_addr_t addr = pfn << PAGE_SHIFT;
@@ -294,7 +293,6 @@ int pfn_valid(unsigned long pfn)
 	return memblock_is_map_memory(addr);
 }
 EXPORT_SYMBOL(pfn_valid);
-#endif
 
 #ifndef CONFIG_SPARSEMEM
 static void __init arm64_memory_present(void)