[PATCH] i386 sparsemem for single node systems

Allow SPARSEMEM to be enabled on non-numa x86 systems.  This is made
dependant on EXPERIMENTAL also being set.  When an in-tree user (such as
simulated numa) exists it should be made dependant on that.

The plan is to have no options and no selector as normal when
!EXPERIMENTAL.  When EXPERIMENTAL we enable the FLATMEM and SPARSEMEM
options for X86_PC whilst maintaining DISCONTIGMEM and SPARSEMEM for NUMA.
Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/i386/Kconfig

@@ -464,7 +464,6 @@ config NUMA
 	depends on SMP && HIGHMEM64G && (X86_NUMAQ || X86_GENERICARCH || (X86_SUMMIT && ACPI))
 	default n if X86_PC
 	default y if (X86_NUMAQ || X86_SUMMIT)
-	select SPARSEMEM_STATIC
 
 # Need comments to help the hapless user trying to turn on NUMA support
 comment "NUMA (NUMA-Q) requires SMP, 64GB highmem support"
@@ -493,6 +492,10 @@ config HAVE_ARCH_ALLOC_REMAP
 	depends on NUMA
 	default y
 
+config ARCH_FLATMEM_ENABLE
+	def_bool y
+	depends on (ARCH_SELECT_MEMORY_MODEL && X86_PC)
+
 config ARCH_DISCONTIGMEM_ENABLE
 	def_bool y
 	depends on NUMA
@@ -503,7 +506,8 @@ config ARCH_DISCONTIGMEM_DEFAULT
 
 config ARCH_SPARSEMEM_ENABLE
 	def_bool y
-	depends on NUMA
+	depends on (NUMA || (X86_PC && EXPERIMENTAL))
+	select SPARSEMEM_STATIC
 
 config ARCH_SELECT_MEMORY_MODEL
 	def_bool y

arch/i386/kernel/setup.c

@@ -954,6 +954,12 @@ efi_find_max_pfn(unsigned long start, unsigned long end, void *arg)
 	return 0;
 }
 
+static int __init
+efi_memory_present_wrapper(unsigned long start, unsigned long end, void *arg)
+{
+	memory_present(0, start, end);
+	return 0;
+}
 
 /*
  * Find the highest page frame number we have available
@@ -965,6 +971,7 @@ void __init find_max_pfn(void)
 	max_pfn = 0;
 	if (efi_enabled) {
 		efi_memmap_walk(efi_find_max_pfn, &max_pfn);
+		efi_memmap_walk(efi_memory_present_wrapper, NULL);
 		return;
 	}
 
@@ -979,6 +986,7 @@ void __init find_max_pfn(void)
 			continue;
 		if (end > max_pfn)
 			max_pfn = end;
+		memory_present(0, start, end);
 	}
 }