x86, ds: use single debug store cpu configuration

Use a single configuration for all cpus.
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
Cc: roland@redhat.com
Cc: eranian@googlemail.com
Cc: oleg@redhat.com
Cc: juan.villacis@intel.com
Cc: ak@linux.jf.intel.com
LKML-Reference: <20090403144602.191165000@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/ds.c

@@ -47,9 +47,8 @@ struct ds_configuration {
 	/* Control bit-masks indexed by enum ds_feature: */
 	unsigned long		ctl[dsf_ctl_max];
 };
-static DEFINE_PER_CPU(struct ds_configuration, ds_cfg_array);
+static struct ds_configuration ds_cfg __read_mostly;
 
-#define ds_cfg per_cpu(ds_cfg_array, smp_processor_id())
 
 /* Maximal size of a DS configuration: */
 #define MAX_SIZEOF_DS		(12 * 8)
@@ -1268,6 +1267,10 @@ ds_configure(const struct ds_configuration *cfg,
 
 void __cpuinit ds_init_intel(struct cpuinfo_x86 *c)
 {
+	/* Only configure the first cpu. Others are identical. */
+	if (ds_cfg.name)
+		return;
+
 	switch (c->x86) {
 	case 0x6:
 		switch (c->x86_model) {