3 files changed, 32 insertions, 0 deletions

diff --git a/arch/x86_64/kernel/setup.c b/arch/x86_64/kernel/setup.c
index 46bf556efc30..173bdc55113b 100644
--- a/arch/x86_64/kernel/setup.c
+++ b/arch/x86_64/kernel/setup.c
@@ -713,6 +713,8 @@ void __init setup_arch(char **cmdline_p)
         acpi_boot_init();
 #endif
 
+        init_cpu_to_node();
+
 #ifdef CONFIG_X86_LOCAL_APIC
         /*
          * get boot-time SMP configuration:
diff --git a/arch/x86_64/mm/numa.c b/arch/x86_64/mm/numa.c
index 42ec1f4f491a..876e34374412 100644
--- a/arch/x86_64/mm/numa.c
+++ b/arch/x86_64/mm/numa.c
@@ -330,6 +330,31 @@ __init int numa_setup(char *opt)
         return 1;
 } 
 
+/*
+ * Setup early cpu_to_node.
+ *
+ * Populate cpu_to_node[] only if x86_cpu_to_apicid[],
+ * and apicid_to_node[] tables have valid entries for a CPU.
+ * This means we skip cpu_to_node[] initialisation for NUMA
+ * emulation and faking node case (when running a kernel compiled
+ * for NUMA on a non NUMA box), which is OK as cpu_to_node[]
+ * is already initialized in a round robin manner at numa_init_array,
+ * prior to this call, and this initialization is good enough
+ * for the fake NUMA cases.
+ */
+void __init init_cpu_to_node(void)
+{
+        int i;
+        for (i = 0; i < NR_CPUS; i++) {
+                u8 apicid = x86_cpu_to_apicid[i];
+                if (apicid == BAD_APICID)
+                        continue;
+                if (apicid_to_node[apicid] == NUMA_NO_NODE)
+                        continue;
+                cpu_to_node[i] = apicid_to_node[apicid];
+        }
+}
+
 EXPORT_SYMBOL(cpu_to_node);
 EXPORT_SYMBOL(node_to_cpumask);
 EXPORT_SYMBOL(memnode_shift);
diff --git a/include/asm-x86_64/numa.h b/include/asm-x86_64/numa.h
index d51e56fdc3da..34e434ce3268 100644
--- a/include/asm-x86_64/numa.h
+++ b/include/asm-x86_64/numa.h
@@ -20,6 +20,11 @@ extern int numa_off;
 extern void numa_set_node(int cpu, int node);
 
 extern unsigned char apicid_to_node[256];
+#ifdef CONFIG_NUMA
+extern void __init init_cpu_to_node(void);
+#else
+#define init_cpu_to_node() do {} while (0)
+#endif
 
 #define NUMA_NO_NODE 0xff