x86: modify Kconfig to allow up to 4096 cpus

  * Increase the limit of NR_CPUS to 4096 and introduce a boolean
    called "MAXSMP" which when set (e.g. "allyesconfig"), will set
    NR_CPUS = 4096 and NODES_SHIFT = 9 (512).

  * Changed max setting for NODES_SHIFT from 15 to 9 to accurately
    reflect the real limit.
Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/Kconfig

@@ -561,20 +561,35 @@ config SWIOTLB
 
 config IOMMU_HELPER
 	def_bool (CALGARY_IOMMU || GART_IOMMU || SWIOTLB)
+config MAXSMP
+	bool "Configure Maximum number of SMP Processors and NUMA Nodes"
+	depends on X86_64 && SMP
+	default n
+	help
+	  Configure maximum number of CPUS and NUMA Nodes for this architecture.
+	  If unsure, say N.
 
+if MAXSMP
 config NR_CPUS
-	int "Maximum number of CPUs (2-255)"
-	range 2 255
+	int
+	default "4096"
+endif
+
+if !MAXSMP
+config NR_CPUS
+	int "Maximum number of CPUs (2-4096)"
+	range 2 4096
 	depends on SMP
 	default "32" if X86_NUMAQ || X86_SUMMIT || X86_BIGSMP || X86_ES7000
 	default "8"
 	help
 	  This allows you to specify the maximum number of CPUs which this
-	  kernel will support.  The maximum supported value is 255 and the
+	  kernel will support.  The maximum supported value is 4096 and the
 	  minimum value which makes sense is 2.
 
 	  This is purely to save memory - each supported CPU adds
 	  approximately eight kilobytes to the kernel image.
+endif
 
 config SCHED_SMT
 	bool "SMT (Hyperthreading) scheduler support"
@@ -965,13 +980,25 @@ config NUMA_EMU
 	  into virtual nodes when booted with "numa=fake=N", where N is the
 	  number of nodes. This is only useful for debugging.
 
+if MAXSMP
+
+config NODES_SHIFT
+	int
+	default "9"
+endif
+
+if !MAXSMP
 config NODES_SHIFT
-	int "Max num nodes shift(1-9)"
+	int "Maximum NUMA Nodes (as a power of 2)"
 	range 1 9   if X86_64
 	default "6" if X86_64
 	default "4" if X86_NUMAQ
 	default "3"
 	depends on NEED_MULTIPLE_NODES
+	help
+	  Specify the maximum number of NUMA Nodes available on the target
+	  system.  Increases memory reserved to accomodate various tables.
+endif
 
 config HAVE_ARCH_BOOTMEM_NODE
 	def_bool y