x86, hotplug: Support functions for CPU0 online/offline

Add smp_store_boot_cpu_info() to store cpu info for BSP during boot time.

Now smp_store_cpu_info() stores cpu info for bringing up BSP or AP after
it's offline.

Continue to online CPU0 in native_cpu_up().

Continue to offline CPU0 in native_cpu_disable().

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Link: http://lkml.kernel.org/r/1352835171-3958-5-git-send-email-fenghua.yu@intel.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

1 files changed, 18 insertions, 20 deletions

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index c80a33bc528b..c297907f3c75 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -125,8 +125,8 @@ EXPORT_PER_CPU_SYMBOL(cpu_info);
 atomic_t init_deasserted;
 
 /*
- * Report back to the Boot Processor.
- * Running on AP.
+ * Report back to the Boot Processor during boot time or to the caller processor
+ * during CPU online.
  */
 static void __cpuinit smp_callin(void)
 {
@@ -279,19 +279,30 @@ notrace static void __cpuinit start_secondary(void *unused)
         cpu_idle();
 }
 
+void __init smp_store_boot_cpu_info(void)
+{
+        int id = 0; /* CPU 0 */
+        struct cpuinfo_x86 *c = &cpu_data(id);
+
+        *c = boot_cpu_data;
+        c->cpu_index = id;
+}
+
 /*
  * The bootstrap kernel entry code has set these up. Save them for
  * a given CPU
  */
-
 void __cpuinit smp_store_cpu_info(int id)
 {
         struct cpuinfo_x86 *c = &cpu_data(id);
 
         *c = boot_cpu_data;
         c->cpu_index = id;
-        if (id != 0)
-                identify_secondary_cpu(c);
+        /*
+         * During boot time, CPU0 has this setup already. Save the info when
+         * bringing up AP or offlined CPU0.
+         */
+        identify_secondary_cpu(c);
 }
 
 static bool __cpuinit
@@ -795,7 +806,7 @@ int __cpuinit native_cpu_up(unsigned int cpu, struct task_struct *tidle)
 
         pr_debug("++++++++++++++++++++=_---CPU UP  %u\n", cpu);
 
-        if (apicid == BAD_APICID || apicid == boot_cpu_physical_apicid ||
+        if (apicid == BAD_APICID ||
             !physid_isset(apicid, phys_cpu_present_map) ||
             !apic->apic_id_valid(apicid)) {
                 pr_err("%s: bad cpu %d\n", __func__, cpu);
@@ -990,7 +1001,7 @@ void __init native_smp_prepare_cpus(unsigned int max_cpus)
         /*
          * Setup boot CPU information
          */
-        smp_store_cpu_info(0); /* Final full version of the data */
+        smp_store_boot_cpu_info(); /* Final full version of the data */
         cpumask_copy(cpu_callin_mask, cpumask_of(0));
         mb();
 
@@ -1214,19 +1225,6 @@ void cpu_disable_common(void)
 
 int native_cpu_disable(void)
 {
-        int cpu = smp_processor_id();
-
-        /*
-         * Perhaps use cpufreq to drop frequency, but that could go
-         * into generic code.
-         *
-         * We won't take down the boot processor on i386 due to some
-         * interrupts only being able to be serviced by the BSP.
-         * Especially so if we're not using an IOAPIC   -zwane
-         */
-        if (cpu == 0)
-                return -EBUSY;
-
         clear_local_APIC();
 
         cpu_disable_common();