1 files changed, 422 insertions, 153 deletions

diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 264ea906db4c..aa37fa154512 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -42,6 +42,7 @@
 #include <asm/tlbflush.h>
 #include <asm/timer.h>
 #include <asm/lowcore.h>
+#include <asm/sclp.h>
 #include <asm/cpu.h>
 
 /*
@@ -53,11 +54,27 @@ EXPORT_SYMBOL(lowcore_ptr);
 cpumask_t cpu_online_map = CPU_MASK_NONE;
 EXPORT_SYMBOL(cpu_online_map);
 
-cpumask_t cpu_possible_map = CPU_MASK_NONE;
+cpumask_t cpu_possible_map = CPU_MASK_ALL;
 EXPORT_SYMBOL(cpu_possible_map);
 
 static struct task_struct *current_set[NR_CPUS];
 
+static u8 smp_cpu_type;
+static int smp_use_sigp_detection;
+
+enum s390_cpu_state {
+        CPU_STATE_STANDBY,
+        CPU_STATE_CONFIGURED,
+};
+
+#ifdef CONFIG_HOTPLUG_CPU
+static DEFINE_MUTEX(smp_cpu_state_mutex);
+#endif
+static int smp_cpu_state[NR_CPUS];
+
+static DEFINE_PER_CPU(struct cpu, cpu_devices);
+DEFINE_PER_CPU(struct s390_idle_data, s390_idle);
+
 static void smp_ext_bitcall(int, ec_bit_sig);
 
 /*
@@ -193,6 +210,33 @@ int smp_call_function_single(int cpu, void (*func) (void *info), void *info,
 }
 EXPORT_SYMBOL(smp_call_function_single);
 
+/**
+ * smp_call_function_mask(): Run a function on a set of other CPUs.
+ * @mask: The set of cpus to run on.  Must not include the current cpu.
+ * @func: The function to run. This must be fast and non-blocking.
+ * @info: An arbitrary pointer to pass to the function.
+ * @wait: If true, wait (atomically) until function has completed on other CPUs.
+ *
+ * Returns 0 on success, else a negative status code.
+ *
+ * If @wait is true, then returns once @func has returned; otherwise
+ * it returns just before the target cpu calls @func.
+ *
+ * You must not call this function with disabled interrupts or from a
+ * hardware interrupt handler or from a bottom half handler.
+ */
+int
+smp_call_function_mask(cpumask_t mask,
+                        void (*func)(void *), void *info,
+                        int wait)
+{
+        preempt_disable();
+        __smp_call_function_map(func, info, 0, wait, mask);
+        preempt_enable();
+        return 0;
+}
+EXPORT_SYMBOL(smp_call_function_mask);
+
 void smp_send_stop(void)
 {
         int cpu, rc;
@@ -217,33 +261,6 @@ void smp_send_stop(void)
 }
 
 /*
- * Reboot, halt and power_off routines for SMP.
- */
-void machine_restart_smp(char *__unused)
-{
-        smp_send_stop();
-        do_reipl();
-}
-
-void machine_halt_smp(void)
-{
-        smp_send_stop();
-        if (MACHINE_IS_VM && strlen(vmhalt_cmd) > 0)
-                __cpcmd(vmhalt_cmd, NULL, 0, NULL);
-        signal_processor(smp_processor_id(), sigp_stop_and_store_status);
-        for (;;);
-}
-
-void machine_power_off_smp(void)
-{
-        smp_send_stop();
-        if (MACHINE_IS_VM && strlen(vmpoff_cmd) > 0)
-                __cpcmd(vmpoff_cmd, NULL, 0, NULL);
-        signal_processor(smp_processor_id(), sigp_stop_and_store_status);
-        for (;;);
-}
-
-/*
  * This is the main routine where commands issued by other
  * cpus are handled.
  */
@@ -355,6 +372,13 @@ void smp_ctl_clear_bit(int cr, int bit)
 }
 EXPORT_SYMBOL(smp_ctl_clear_bit);
 
+/*
+ * In early ipl state a temp. logically cpu number is needed, so the sigp
+ * functions can be used to sense other cpus. Since NR_CPUS is >= 2 on
+ * CONFIG_SMP and the ipl cpu is logical cpu 0, it must be 1.
+ */
+#define CPU_INIT_NO     1
+
 #if defined(CONFIG_ZFCPDUMP) || defined(CONFIG_ZFCPDUMP_MODULE)
 
 /*
@@ -375,9 +399,10 @@ static void __init smp_get_save_area(unsigned int cpu, unsigned int phy_cpu)
                        "kernel was compiled with NR_CPUS=%i\n", cpu, NR_CPUS);
                 return;
         }
-        zfcpdump_save_areas[cpu] = alloc_bootmem(sizeof(union save_area));
-        __cpu_logical_map[1] = (__u16) phy_cpu;
-        while (signal_processor(1, sigp_stop_and_store_status) == sigp_busy)
+        zfcpdump_save_areas[cpu] = kmalloc(sizeof(union save_area), GFP_KERNEL);
+        __cpu_logical_map[CPU_INIT_NO] = (__u16) phy_cpu;
+        while (signal_processor(CPU_INIT_NO, sigp_stop_and_store_status) ==
+               sigp_busy)
                 cpu_relax();
         memcpy(zfcpdump_save_areas[cpu],
                (void *)(unsigned long) store_prefix() + SAVE_AREA_BASE,
@@ -397,32 +422,155 @@ static inline void smp_get_save_area(unsigned int cpu, unsigned int phy_cpu) { }
 
 #endif /* CONFIG_ZFCPDUMP || CONFIG_ZFCPDUMP_MODULE */
 
-/*
- * Lets check how many CPUs we have.
- */
-static unsigned int __init smp_count_cpus(void)
+static int cpu_stopped(int cpu)
 {
-        unsigned int cpu, num_cpus;
-        __u16 boot_cpu_addr;
+        __u32 status;
 
-        /*
-         * cpu 0 is the boot cpu. See smp_prepare_boot_cpu.
-         */
+        /* Check for stopped state */
+        if (signal_processor_ps(&status, 0, cpu, sigp_sense) ==
+            sigp_status_stored) {
+                if (status & 0x40)
+                        return 1;
+        }
+        return 0;
+}
+
+static int cpu_known(int cpu_id)
+{
+        int cpu;
+
+        for_each_present_cpu(cpu) {
+                if (__cpu_logical_map[cpu] == cpu_id)
+                        return 1;
+        }
+        return 0;
+}
+
+static int smp_rescan_cpus_sigp(cpumask_t avail)
+{
+        int cpu_id, logical_cpu;
+
+        logical_cpu = first_cpu(avail);
+        if (logical_cpu == NR_CPUS)
+                return 0;
+        for (cpu_id = 0; cpu_id <= 65535; cpu_id++) {
+                if (cpu_known(cpu_id))
+                        continue;
+                __cpu_logical_map[logical_cpu] = cpu_id;
+                if (!cpu_stopped(logical_cpu))
+                        continue;
+                cpu_set(logical_cpu, cpu_present_map);
+                smp_cpu_state[logical_cpu] = CPU_STATE_CONFIGURED;
+                logical_cpu = next_cpu(logical_cpu, avail);
+                if (logical_cpu == NR_CPUS)
+                        break;
+        }
+        return 0;
+}
+
+static int smp_rescan_cpus_sclp(cpumask_t avail)
+{
+        struct sclp_cpu_info *info;
+        int cpu_id, logical_cpu, cpu;
+        int rc;
+
+        logical_cpu = first_cpu(avail);
+        if (logical_cpu == NR_CPUS)
+                return 0;
+        info = kmalloc(sizeof(*info), GFP_KERNEL);
+        if (!info)
+                return -ENOMEM;
+        rc = sclp_get_cpu_info(info);
+        if (rc)
+                goto out;
+        for (cpu = 0; cpu < info->combined; cpu++) {
+                if (info->has_cpu_type && info->cpu[cpu].type != smp_cpu_type)
+                        continue;
+                cpu_id = info->cpu[cpu].address;
+                if (cpu_known(cpu_id))
+                        continue;
+                __cpu_logical_map[logical_cpu] = cpu_id;
+                cpu_set(logical_cpu, cpu_present_map);
+                if (cpu >= info->configured)
+                        smp_cpu_state[logical_cpu] = CPU_STATE_STANDBY;
+                else
+                        smp_cpu_state[logical_cpu] = CPU_STATE_CONFIGURED;
+                logical_cpu = next_cpu(logical_cpu, avail);
+                if (logical_cpu == NR_CPUS)
+                        break;
+        }
+out:
+        kfree(info);
+        return rc;
+}
+
+static int smp_rescan_cpus(void)
+{
+        cpumask_t avail;
+
+        cpus_xor(avail, cpu_possible_map, cpu_present_map);
+        if (smp_use_sigp_detection)
+                return smp_rescan_cpus_sigp(avail);
+        else
+                return smp_rescan_cpus_sclp(avail);
+}
+
+static void __init smp_detect_cpus(void)
+{
+        unsigned int cpu, c_cpus, s_cpus;
+        struct sclp_cpu_info *info;
+        u16 boot_cpu_addr, cpu_addr;
+
+        c_cpus = 1;
+        s_cpus = 0;
         boot_cpu_addr = S390_lowcore.cpu_data.cpu_addr;
-        current_thread_info()->cpu = 0;
-        num_cpus = 1;
-        for (cpu = 0; cpu <= 65535; cpu++) {
-                if ((__u16) cpu == boot_cpu_addr)
+        info = kmalloc(sizeof(*info), GFP_KERNEL);
+        if (!info)
+                panic("smp_detect_cpus failed to allocate memory\n");
+        /* Use sigp detection algorithm if sclp doesn't work. */
+        if (sclp_get_cpu_info(info)) {
+                smp_use_sigp_detection = 1;
+                for (cpu = 0; cpu <= 65535; cpu++) {
+                        if (cpu == boot_cpu_addr)
+                                continue;
+                        __cpu_logical_map[CPU_INIT_NO] = cpu;
+                        if (!cpu_stopped(CPU_INIT_NO))
+                                continue;
+                        smp_get_save_area(c_cpus, cpu);
+                        c_cpus++;
+                }
+                goto out;
+        }
+
+        if (info->has_cpu_type) {
+                for (cpu = 0; cpu < info->combined; cpu++) {
+                        if (info->cpu[cpu].address == boot_cpu_addr) {
+                                smp_cpu_type = info->cpu[cpu].type;
+                                break;
+                        }
+                }
+        }
+
+        for (cpu = 0; cpu < info->combined; cpu++) {
+                if (info->has_cpu_type && info->cpu[cpu].type != smp_cpu_type)
+                        continue;
+                cpu_addr = info->cpu[cpu].address;
+                if (cpu_addr == boot_cpu_addr)
                         continue;
-                __cpu_logical_map[1] = (__u16) cpu;
-                if (signal_processor(1, sigp_sense) == sigp_not_operational)
+                __cpu_logical_map[CPU_INIT_NO] = cpu_addr;
+                if (!cpu_stopped(CPU_INIT_NO)) {
+                        s_cpus++;
                         continue;
-                smp_get_save_area(num_cpus, cpu);
-                num_cpus++;
+                }
+                smp_get_save_area(c_cpus, cpu_addr);
+                c_cpus++;
         }
-        printk("Detected %d CPU's\n", (int) num_cpus);
-        printk("Boot cpu address %2X\n", boot_cpu_addr);
-        return num_cpus;
+out:
+        kfree(info);
+        printk(KERN_INFO "CPUs: %d configured, %d standby\n", c_cpus, s_cpus);
+        get_online_cpus();
+        smp_rescan_cpus();
+        put_online_cpus();
 }
 
 /*
@@ -453,8 +601,6 @@ int __cpuinit start_secondary(void *cpuvoid)
         return 0;
 }
 
-DEFINE_PER_CPU(struct s390_idle_data, s390_idle);
-
 static void __init smp_create_idle(unsigned int cpu)
 {
         struct task_struct *p;
@@ -470,37 +616,82 @@ static void __init smp_create_idle(unsigned int cpu)
         spin_lock_init(&(&per_cpu(s390_idle, cpu))->lock);
 }
 
-static int cpu_stopped(int cpu)
+static int __cpuinit smp_alloc_lowcore(int cpu)
 {
-        __u32 status;
+        unsigned long async_stack, panic_stack;
+        struct _lowcore *lowcore;
+        int lc_order;
+
+        lc_order = sizeof(long) == 8 ? 1 : 0;
+        lowcore = (void *) __get_free_pages(GFP_KERNEL | GFP_DMA, lc_order);
+        if (!lowcore)
+                return -ENOMEM;
+        async_stack = __get_free_pages(GFP_KERNEL, ASYNC_ORDER);
+        if (!async_stack)
+                goto out_async_stack;
+        panic_stack = __get_free_page(GFP_KERNEL);
+        if (!panic_stack)
+                goto out_panic_stack;
+
+        *lowcore = S390_lowcore;
+        lowcore->async_stack = async_stack + ASYNC_SIZE;
+        lowcore->panic_stack = panic_stack + PAGE_SIZE;
 
-        /* Check for stopped state */
-        if (signal_processor_ps(&status, 0, cpu, sigp_sense) ==
-            sigp_status_stored) {
-                if (status & 0x40)
-                        return 1;
+#ifndef CONFIG_64BIT
+        if (MACHINE_HAS_IEEE) {
+                unsigned long save_area;
+
+                save_area = get_zeroed_page(GFP_KERNEL);
+                if (!save_area)
+                        goto out_save_area;
+                lowcore->extended_save_area_addr = (u32) save_area;
         }
+#endif
+        lowcore_ptr[cpu] = lowcore;
         return 0;
+
+#ifndef CONFIG_64BIT
+out_save_area:
+        free_page(panic_stack);
+#endif
+out_panic_stack:
+        free_pages(async_stack, ASYNC_ORDER);
+out_async_stack:
+        free_pages((unsigned long) lowcore, lc_order);
+        return -ENOMEM;
 }
 
-/* Upping and downing of CPUs */
+#ifdef CONFIG_HOTPLUG_CPU
+static void smp_free_lowcore(int cpu)
+{
+        struct _lowcore *lowcore;
+        int lc_order;
+
+        lc_order = sizeof(long) == 8 ? 1 : 0;
+        lowcore = lowcore_ptr[cpu];
+#ifndef CONFIG_64BIT
+        if (MACHINE_HAS_IEEE)
+                free_page((unsigned long) lowcore->extended_save_area_addr);
+#endif
+        free_page(lowcore->panic_stack - PAGE_SIZE);
+        free_pages(lowcore->async_stack - ASYNC_SIZE, ASYNC_ORDER);
+        free_pages((unsigned long) lowcore, lc_order);
+        lowcore_ptr[cpu] = NULL;
+}
+#endif /* CONFIG_HOTPLUG_CPU */
 
-int __cpu_up(unsigned int cpu)
+/* Upping and downing of CPUs */
+int __cpuinit __cpu_up(unsigned int cpu)
 {
         struct task_struct *idle;
         struct _lowcore *cpu_lowcore;
         struct stack_frame *sf;
         sigp_ccode ccode;
-        int curr_cpu;
 
-        for (curr_cpu = 0; curr_cpu <= 65535; curr_cpu++) {
-                __cpu_logical_map[cpu] = (__u16) curr_cpu;
-                if (cpu_stopped(cpu))
-                        break;
-        }
-
-        if (!cpu_stopped(cpu))
-                return -ENODEV;
+        if (smp_cpu_state[cpu] != CPU_STATE_CONFIGURED)
+                return -EIO;
+        if (smp_alloc_lowcore(cpu))
+                return -ENOMEM;
 
         ccode = signal_processor_p((__u32)(unsigned long)(lowcore_ptr[cpu]),
                                    cpu, sigp_set_prefix);
@@ -515,6 +706,7 @@ int __cpu_up(unsigned int cpu)
         cpu_lowcore = lowcore_ptr[cpu];
         cpu_lowcore->kernel_stack = (unsigned long)
                 task_stack_page(idle) + THREAD_SIZE;
+        cpu_lowcore->thread_info = (unsigned long) task_thread_info(idle);
         sf = (struct stack_frame *) (cpu_lowcore->kernel_stack
                                      - sizeof(struct pt_regs)
                                      - sizeof(struct stack_frame));
@@ -528,6 +720,8 @@ int __cpu_up(unsigned int cpu)
         cpu_lowcore->percpu_offset = __per_cpu_offset[cpu];
         cpu_lowcore->current_task = (unsigned long) idle;
         cpu_lowcore->cpu_data.cpu_nr = cpu;
+        cpu_lowcore->softirq_pending = 0;
+        cpu_lowcore->ext_call_fast = 0;
         eieio();
 
         while (signal_processor(cpu, sigp_restart) == sigp_busy)
@@ -538,44 +732,20 @@ int __cpu_up(unsigned int cpu)
         return 0;
 }
 
-static unsigned int __initdata additional_cpus;
-static unsigned int __initdata possible_cpus;
-
-void __init smp_setup_cpu_possible_map(void)
+static int __init setup_possible_cpus(char *s)
 {
-        unsigned int phy_cpus, pos_cpus, cpu;
-
-        phy_cpus = smp_count_cpus();
-        pos_cpus = min(phy_cpus + additional_cpus, (unsigned int) NR_CPUS);
-
-        if (possible_cpus)
-                pos_cpus = min(possible_cpus, (unsigned int) NR_CPUS);
+        int pcpus, cpu;
 
-        for (cpu = 0; cpu < pos_cpus; cpu++)
+        pcpus = simple_strtoul(s, NULL, 0);
+        cpu_possible_map = cpumask_of_cpu(0);
+        for (cpu = 1; cpu < pcpus && cpu < NR_CPUS; cpu++)
                 cpu_set(cpu, cpu_possible_map);
-
-        phy_cpus = min(phy_cpus, pos_cpus);
-
-        for (cpu = 0; cpu < phy_cpus; cpu++)
-                cpu_set(cpu, cpu_present_map);
-}
-
-#ifdef CONFIG_HOTPLUG_CPU
-
-static int __init setup_additional_cpus(char *s)
-{
-        additional_cpus = simple_strtoul(s, NULL, 0);
-        return 0;
-}
-early_param("additional_cpus", setup_additional_cpus);
-
-static int __init setup_possible_cpus(char *s)
-{
-        possible_cpus = simple_strtoul(s, NULL, 0);
         return 0;
 }
 early_param("possible_cpus", setup_possible_cpus);
 
+#ifdef CONFIG_HOTPLUG_CPU
+
 int __cpu_disable(void)
 {
         struct ec_creg_mask_parms cr_parms;
@@ -612,7 +782,8 @@ void __cpu_die(unsigned int cpu)
         /* Wait until target cpu is down */
         while (!smp_cpu_not_running(cpu))
                 cpu_relax();
-        printk("Processor %d spun down\n", cpu);
+        smp_free_lowcore(cpu);
+        printk(KERN_INFO "Processor %d spun down\n", cpu);
 }
 
 void cpu_die(void)
@@ -625,49 +796,19 @@ void cpu_die(void)
 
 #endif /* CONFIG_HOTPLUG_CPU */
 
-/*
- *      Cycle through the processors and setup structures.
- */
-
 void __init smp_prepare_cpus(unsigned int max_cpus)
 {
-        unsigned long stack;
         unsigned int cpu;
-        int i;
+
+        smp_detect_cpus();
 
         /* request the 0x1201 emergency signal external interrupt */
         if (register_external_interrupt(0x1201, do_ext_call_interrupt) != 0)
                 panic("Couldn't request external interrupt 0x1201");
         memset(lowcore_ptr, 0, sizeof(lowcore_ptr));
-        /*
-         *  Initialize prefix pages and stacks for all possible cpus
-         */
         print_cpu_info(&S390_lowcore.cpu_data);
+        smp_alloc_lowcore(smp_processor_id());
 
-        for_each_possible_cpu(i) {
-                lowcore_ptr[i] = (struct _lowcore *)
-                        __get_free_pages(GFP_KERNEL | GFP_DMA,
-                                         sizeof(void*) == 8 ? 1 : 0);
-                stack = __get_free_pages(GFP_KERNEL, ASYNC_ORDER);
-                if (!lowcore_ptr[i] || !stack)
-                        panic("smp_boot_cpus failed to allocate memory\n");
-
-                *(lowcore_ptr[i]) = S390_lowcore;
-                lowcore_ptr[i]->async_stack = stack + ASYNC_SIZE;
-                stack = __get_free_pages(GFP_KERNEL, 0);
-                if (!stack)
-                        panic("smp_boot_cpus failed to allocate memory\n");
-                lowcore_ptr[i]->panic_stack = stack + PAGE_SIZE;
-#ifndef CONFIG_64BIT
-                if (MACHINE_HAS_IEEE) {
-                        lowcore_ptr[i]->extended_save_area_addr =
-                                (__u32) __get_free_pages(GFP_KERNEL, 0);
-                        if (!lowcore_ptr[i]->extended_save_area_addr)
-                                panic("smp_boot_cpus failed to "
-                                      "allocate memory\n");
-                }
-#endif
-        }
 #ifndef CONFIG_64BIT
         if (MACHINE_HAS_IEEE)
                 ctl_set_bit(14, 29); /* enable extended save area */
@@ -683,15 +824,17 @@ void __init smp_prepare_boot_cpu(void)
 {
         BUG_ON(smp_processor_id() != 0);
 
+        current_thread_info()->cpu = 0;
+        cpu_set(0, cpu_present_map);
         cpu_set(0, cpu_online_map);
         S390_lowcore.percpu_offset = __per_cpu_offset[0];
         current_set[0] = current;
+        smp_cpu_state[0] = CPU_STATE_CONFIGURED;
         spin_lock_init(&(&__get_cpu_var(s390_idle))->lock);
 }
 
 void __init smp_cpus_done(unsigned int max_cpus)
 {
-        cpu_present_map = cpu_possible_map;
 }
 
 /*
@@ -705,7 +848,79 @@ int setup_profiling_timer(unsigned int multiplier)
         return 0;
 }
 
-static DEFINE_PER_CPU(struct cpu, cpu_devices);
+#ifdef CONFIG_HOTPLUG_CPU
+static ssize_t cpu_configure_show(struct sys_device *dev, char *buf)
+{
+        ssize_t count;
+
+        mutex_lock(&smp_cpu_state_mutex);
+        count = sprintf(buf, "%d\n", smp_cpu_state[dev->id]);
+        mutex_unlock(&smp_cpu_state_mutex);
+        return count;
+}
+
+static ssize_t cpu_configure_store(struct sys_device *dev, const char *buf,
+                                   size_t count)
+{
+        int cpu = dev->id;
+        int val, rc;
+        char delim;
+
+        if (sscanf(buf, "%d %c", &val, &delim) != 1)
+                return -EINVAL;
+        if (val != 0 && val != 1)
+                return -EINVAL;
+
+        mutex_lock(&smp_cpu_state_mutex);
+        get_online_cpus();
+        rc = -EBUSY;
+        if (cpu_online(cpu))
+                goto out;
+        rc = 0;
+        switch (val) {
+        case 0:
+                if (smp_cpu_state[cpu] == CPU_STATE_CONFIGURED) {
+                        rc = sclp_cpu_deconfigure(__cpu_logical_map[cpu]);
+                        if (!rc)
+                                smp_cpu_state[cpu] = CPU_STATE_STANDBY;
+                }
+                break;
+        case 1:
+                if (smp_cpu_state[cpu] == CPU_STATE_STANDBY) {
+                        rc = sclp_cpu_configure(__cpu_logical_map[cpu]);
+                        if (!rc)
+                                smp_cpu_state[cpu] = CPU_STATE_CONFIGURED;
+                }
+                break;
+        default:
+                break;
+        }
+out:
+        put_online_cpus();
+        mutex_unlock(&smp_cpu_state_mutex);
+        return rc ? rc : count;
+}
+static SYSDEV_ATTR(configure, 0644, cpu_configure_show, cpu_configure_store);
+#endif /* CONFIG_HOTPLUG_CPU */
+
+static ssize_t show_cpu_address(struct sys_device *dev, char *buf)
+{
+        return sprintf(buf, "%d\n", __cpu_logical_map[dev->id]);
+}
+static SYSDEV_ATTR(address, 0444, show_cpu_address, NULL);
+
+
+static struct attribute *cpu_common_attrs[] = {
+#ifdef CONFIG_HOTPLUG_CPU
+        &attr_configure.attr,
+#endif
+        &attr_address.attr,
+        NULL,
+};
+
+static struct attribute_group cpu_common_attr_group = {
+        .attrs = cpu_common_attrs,
+};
 
 static ssize_t show_capability(struct sys_device *dev, char *buf)
 {
@@ -750,15 +965,15 @@ static ssize_t show_idle_time(struct sys_device *dev, char *buf)
 }
 static SYSDEV_ATTR(idle_time_us, 0444, show_idle_time, NULL);
 
-static struct attribute *cpu_attrs[] = {
+static struct attribute *cpu_online_attrs[] = {
         &attr_capability.attr,
         &attr_idle_count.attr,
         &attr_idle_time_us.attr,
         NULL,
 };
 
-static struct attribute_group cpu_attr_group = {
-        .attrs = cpu_attrs,
+static struct attribute_group cpu_online_attr_group = {
+        .attrs = cpu_online_attrs,
 };
 
 static int __cpuinit smp_cpu_notify(struct notifier_block *self,
@@ -778,12 +993,12 @@ static int __cpuinit smp_cpu_notify(struct notifier_block *self,
                 idle->idle_time = 0;
                 idle->idle_count = 0;
                 spin_unlock_irq(&idle->lock);
-                if (sysfs_create_group(&s->kobj, &cpu_attr_group))
+                if (sysfs_create_group(&s->kobj, &cpu_online_attr_group))
                         return NOTIFY_BAD;
                 break;
         case CPU_DEAD:
         case CPU_DEAD_FROZEN:
-                sysfs_remove_group(&s->kobj, &cpu_attr_group);
+                sysfs_remove_group(&s->kobj, &cpu_online_attr_group);
                 break;
         }
         return NOTIFY_OK;
@@ -793,6 +1008,62 @@ static struct notifier_block __cpuinitdata smp_cpu_nb = {
         .notifier_call = smp_cpu_notify,
 };
 
+static int smp_add_present_cpu(int cpu)
+{
+        struct cpu *c = &per_cpu(cpu_devices, cpu);
+        struct sys_device *s = &c->sysdev;
+        int rc;
+
+        c->hotpluggable = 1;
+        rc = register_cpu(c, cpu);
+        if (rc)
+                goto out;
+        rc = sysfs_create_group(&s->kobj, &cpu_common_attr_group);
+        if (rc)
+                goto out_cpu;
+        if (!cpu_online(cpu))
+                goto out;
+        rc = sysfs_create_group(&s->kobj, &cpu_online_attr_group);
+        if (!rc)
+                return 0;
+        sysfs_remove_group(&s->kobj, &cpu_common_attr_group);
+out_cpu:
+#ifdef CONFIG_HOTPLUG_CPU
+        unregister_cpu(c);
+#endif
+out:
+        return rc;
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
+static ssize_t rescan_store(struct sys_device *dev, const char *buf,
+                            size_t count)
+{
+        cpumask_t newcpus;
+        int cpu;
+        int rc;
+
+        mutex_lock(&smp_cpu_state_mutex);
+        get_online_cpus();
+        newcpus = cpu_present_map;
+        rc = smp_rescan_cpus();
+        if (rc)
+                goto out;
+        cpus_andnot(newcpus, cpu_present_map, newcpus);
+        for_each_cpu_mask(cpu, newcpus) {
+                rc = smp_add_present_cpu(cpu);
+                if (rc)
+                        cpu_clear(cpu, cpu_present_map);
+        }
+        rc = 0;
+out:
+        put_online_cpus();
+        mutex_unlock(&smp_cpu_state_mutex);
+        return rc ? rc : count;
+}
+static SYSDEV_ATTR(rescan, 0200, NULL, rescan_store);
+#endif /* CONFIG_HOTPLUG_CPU */
+
 static int __init topology_init(void)
 {
         int cpu;
@@ -800,16 +1071,14 @@ static int __init topology_init(void)
 
         register_cpu_notifier(&smp_cpu_nb);
 
-        for_each_possible_cpu(cpu) {
-                struct cpu *c = &per_cpu(cpu_devices, cpu);
-                struct sys_device *s = &c->sysdev;
-
-                c->hotpluggable = 1;
-                register_cpu(c, cpu);
-                if (!cpu_online(cpu))
-                        continue;
-                s = &c->sysdev;
-                rc = sysfs_create_group(&s->kobj, &cpu_attr_group);
+#ifdef CONFIG_HOTPLUG_CPU
+        rc = sysfs_create_file(&cpu_sysdev_class.kset.kobj,
+                               &attr_rescan.attr);
+        if (rc)
+                return rc;
+#endif
+        for_each_present_cpu(cpu) {
+                rc = smp_add_present_cpu(cpu);
                 if (rc)
                         return rc;
         }