3 files changed, 22 insertions, 0 deletions

diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index 88420af98140..0a82b889d76e 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -47,6 +47,18 @@ config DEBUG_PAGEALLOC
           This results in a large slowdown, but helps to find certain types
           of memory corruptions.
 
+config DEBUG_PER_CPU_MAPS
+        bool "Debug access to per_cpu maps"
+        depends on DEBUG_KERNEL
+        depends on X86_64_SMP
+        default n
+        help
+          Say Y to verify that the per_cpu map being accessed has
+          been setup.  Adds a fair amount of code to kernel memory
+          and decreases performance.
+
+          Say N if unsure.
+
 config DEBUG_RODATA
         bool "Write protect kernel read-only data structures"
         depends on DEBUG_KERNEL
diff --git a/arch/x86/mm/numa_64.c b/arch/x86/mm/numa_64.c
index 5d24dc1ec237..e157cb274b25 100644
--- a/arch/x86/mm/numa_64.c
+++ b/arch/x86/mm/numa_64.c
@@ -37,6 +37,9 @@ u16 x86_cpu_to_node_map_init[NR_CPUS] = {
 void *x86_cpu_to_node_map_early_ptr;
 DEFINE_PER_CPU(u16, x86_cpu_to_node_map) = NUMA_NO_NODE;
 EXPORT_PER_CPU_SYMBOL(x86_cpu_to_node_map);
+#ifdef  CONFIG_DEBUG_PER_CPU_MAPS
+EXPORT_SYMBOL(x86_cpu_to_node_map_early_ptr);
+#endif
 
 u16 apicid_to_node[MAX_LOCAL_APIC] __cpuinitdata = {
         [0 ... MAX_LOCAL_APIC-1] = NUMA_NO_NODE
diff --git a/include/asm-x86/topology.h b/include/asm-x86/topology.h
index 040374f030cf..f1e12329078e 100644
--- a/include/asm-x86/topology.h
+++ b/include/asm-x86/topology.h
@@ -66,6 +66,13 @@ static inline int early_cpu_to_node(int cpu)
 
 static inline int cpu_to_node(int cpu)
 {
+#ifdef  CONFIG_DEBUG_PER_CPU_MAPS
+        if(x86_cpu_to_node_map_early_ptr) {
+                printk("KERN_NOTICE cpu_to_node(%d): usage too early!\n",
+                        (int)cpu);
+                BUG();
+        }
+#endif
         if(per_cpu_offset(cpu))
                 return per_cpu(x86_cpu_to_node_map, cpu);
         else