[safe/jmp/linux-2.6] / arch / s390 / kernel / smp.c

/*
 *  arch/s390/kernel/smp.c
 *
 *    Copyright IBM Corp. 1999,2007
 *    Author(s): Denis Joseph Barrow (djbarrow@de.ibm.com,barrow_dj@yahoo.com),
 *               Martin Schwidefsky (schwidefsky@de.ibm.com)
 *               Heiko Carstens (heiko.carstens@de.ibm.com)
 *
 *  based on other smp stuff by
 *    (c) 1995 Alan Cox, CymruNET Ltd  <alan@cymru.net>
 *    (c) 1998 Ingo Molnar
 *
 * We work with logical cpu numbering everywhere we can. The only
 * functions using the real cpu address (got from STAP) are the sigp
 * functions. For all other functions we use the identity mapping.
 * That means that cpu_number_map[i] == i for every cpu. cpu_number_map is
 * used e.g. to find the idle task belonging to a logical cpu. Every array
 * in the kernel is sorted by the logical cpu number and not by the physical
 * one which is causing all the confusion with __cpu_logical_map and
 * cpu_number_map in other architectures.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/spinlock.h>
#include <linux/kernel_stat.h>
#include <linux/smp_lock.h>
#include <linux/delay.h>
#include <linux/cache.h>
#include <linux/interrupt.h>
#include <linux/cpu.h>
#include <linux/timex.h>
#include <linux/bootmem.h>
#include <asm/ipl.h>
#include <asm/setup.h>
#include <asm/sigp.h>
#include <asm/pgalloc.h>
#include <asm/irq.h>
#include <asm/s390_ext.h>
#include <asm/cpcmd.h>
#include <asm/tlbflush.h>
#include <asm/timer.h>
#include <asm/lowcore.h>

/*
 * An array with a pointer the lowcore of every CPU.
 */
struct _lowcore *lowcore_ptr[NR_CPUS];
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;
EXPORT_SYMBOL(cpu_possible_map);

static struct task_struct *current_set[NR_CPUS];

static void smp_ext_bitcall(int, ec_bit_sig);

/*
 * Structure and data for __smp_call_function_map(). This is designed to
 * minimise static memory requirements. It also looks cleaner.
 */
static DEFINE_SPINLOCK(call_lock);

struct call_data_struct {
        void (*func) (void *info);
        void *info;
        cpumask_t started;
        cpumask_t finished;
        int wait;
};

static struct call_data_struct *call_data;

/*
 * 'Call function' interrupt callback
 */
static void do_call_function(void)
{
        void (*func) (void *info) = call_data->func;
        void *info = call_data->info;
        int wait = call_data->wait;

        cpu_set(smp_processor_id(), call_data->started);
        (*func)(info);
        if (wait)
                cpu_set(smp_processor_id(), call_data->finished);;
}

static void __smp_call_function_map(void (*func) (void *info), void *info,
                                    int nonatomic, int wait, cpumask_t map)
{
        struct call_data_struct data;
        int cpu, local = 0;

        /*
         * Can deadlock when interrupts are disabled or if in wrong context.
         */
        WARN_ON(irqs_disabled() || in_irq());

        /*
         * Check for local function call. We have to have the same call order
         * as in on_each_cpu() because of machine_restart_smp().
         */
        if (cpu_isset(smp_processor_id(), map)) {
                local = 1;
                cpu_clear(smp_processor_id(), map);
        }

        cpus_and(map, map, cpu_online_map);
        if (cpus_empty(map))
                goto out;

        data.func = func;
        data.info = info;
        data.started = CPU_MASK_NONE;
        data.wait = wait;
        if (wait)
                data.finished = CPU_MASK_NONE;

        spin_lock_bh(&call_lock);
        call_data = &data;

        for_each_cpu_mask(cpu, map)
                smp_ext_bitcall(cpu, ec_call_function);

        /* Wait for response */
        while (!cpus_equal(map, data.started))
                cpu_relax();

        if (wait)
                while (!cpus_equal(map, data.finished))
                        cpu_relax();

        spin_unlock_bh(&call_lock);

out:
        local_irq_disable();
        if (local)
                func(info);
        local_irq_enable();
}

/*
 * smp_call_function:
 * @func: the function to run; this must be fast and non-blocking
 * @info: an arbitrary pointer to pass to the function
 * @nonatomic: unused
 * @wait: if true, wait (atomically) until function has completed on other CPUs
 *
 * Run a function on all other CPUs.
 *
 * You must not call this function with disabled interrupts, from a
 * hardware interrupt handler or from a bottom half.
 */
int smp_call_function(void (*func) (void *info), void *info, int nonatomic,
                      int wait)
{
        cpumask_t map;

        preempt_disable();
        map = cpu_online_map;
        cpu_clear(smp_processor_id(), map);
        __smp_call_function_map(func, info, nonatomic, wait, map);
        preempt_enable();
        return 0;
}
EXPORT_SYMBOL(smp_call_function);

/*
 * smp_call_function_on:
 * @func: the function to run; this must be fast and non-blocking
 * @info: an arbitrary pointer to pass to the function
 * @nonatomic: unused
 * @wait: if true, wait (atomically) until function has completed on other CPUs
 * @cpu: the CPU where func should run
 *
 * Run a function on one processor.
 *
 * You must not call this function with disabled interrupts, from a
 * hardware interrupt handler or from a bottom half.
 */
int smp_call_function_on(void (*func) (void *info), void *info, int nonatomic,
                         int wait, int cpu)
{
        cpumask_t map = CPU_MASK_NONE;

        preempt_disable();
        cpu_set(cpu, map);
        __smp_call_function_map(func, info, nonatomic, wait, map);
        preempt_enable();
        return 0;
}
EXPORT_SYMBOL(smp_call_function_on);

static void do_send_stop(void)
{
        int cpu, rc;

        /* stop all processors */
        for_each_online_cpu(cpu) {
                if (cpu == smp_processor_id())
                        continue;
                do {
                        rc = signal_processor(cpu, sigp_stop);
                } while (rc == sigp_busy);
        }
}

static void do_store_status(void)
{
        int cpu, rc;

        /* store status of all processors in their lowcores (real 0) */
        for_each_online_cpu(cpu) {
                if (cpu == smp_processor_id())
                        continue;
                do {
                        rc = signal_processor_p(
                                (__u32)(unsigned long) lowcore_ptr[cpu], cpu,
                                sigp_store_status_at_address);
                } while (rc == sigp_busy);
        }
}

static void do_wait_for_stop(void)
{
        int cpu;

        /* Wait for all other cpus to enter stopped state */
        for_each_online_cpu(cpu) {
                if (cpu == smp_processor_id())
                        continue;
                while (!smp_cpu_not_running(cpu))
                        cpu_relax();
        }
}

/*
 * this function sends a 'stop' sigp to all other CPUs in the system.
 * it goes straight through.
 */
void smp_send_stop(void)
{
        /* Disable all interrupts/machine checks */
        __load_psw_mask(psw_kernel_bits & ~PSW_MASK_MCHECK);

        /* write magic number to zero page (absolute 0) */
        lowcore_ptr[smp_processor_id()]->panic_magic = __PANIC_MAGIC;

        /* stop other processors. */
        do_send_stop();

        /* wait until other processors are stopped */
        do_wait_for_stop();

        /* store status of other processors. */
        do_store_status();
}

/*
 * 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.
 */

static void do_ext_call_interrupt(__u16 code)
{
        unsigned long bits;

        /*
         * handle bit signal external calls
         *
         * For the ec_schedule signal we have to do nothing. All the work
         * is done automatically when we return from the interrupt.
         */
        bits = xchg(&S390_lowcore.ext_call_fast, 0);

        if (test_bit(ec_call_function, &bits))
                do_call_function();
}

/*
 * Send an external call sigp to another cpu and return without waiting
 * for its completion.
 */
static void smp_ext_bitcall(int cpu, ec_bit_sig sig)
{
        /*
         * Set signaling bit in lowcore of target cpu and kick it
         */
        set_bit(sig, (unsigned long *) &lowcore_ptr[cpu]->ext_call_fast);
        while (signal_processor(cpu, sigp_emergency_signal) == sigp_busy)
                udelay(10);
}

#ifndef CONFIG_64BIT
/*
 * this function sends a 'purge tlb' signal to another CPU.
 */
void smp_ptlb_callback(void *info)
{
        local_flush_tlb();
}

void smp_ptlb_all(void)
{
        on_each_cpu(smp_ptlb_callback, NULL, 0, 1);
}
EXPORT_SYMBOL(smp_ptlb_all);
#endif /* ! CONFIG_64BIT */

/*
 * this function sends a 'reschedule' IPI to another CPU.
 * it goes straight through and wastes no time serializing
 * anything. Worst case is that we lose a reschedule ...
 */
void smp_send_reschedule(int cpu)
{
        smp_ext_bitcall(cpu, ec_schedule);
}

/*
 * parameter area for the set/clear control bit callbacks
 */
struct ec_creg_mask_parms {
        unsigned long orvals[16];
        unsigned long andvals[16];
};

/*
 * callback for setting/clearing control bits
 */
static void smp_ctl_bit_callback(void *info)
{
        struct ec_creg_mask_parms *pp = info;
        unsigned long cregs[16];
        int i;

        __ctl_store(cregs, 0, 15);
        for (i = 0; i <= 15; i++)
                cregs[i] = (cregs[i] & pp->andvals[i]) | pp->orvals[i];
        __ctl_load(cregs, 0, 15);
}

/*
 * Set a bit in a control register of all cpus
 */
void smp_ctl_set_bit(int cr, int bit)
{
        struct ec_creg_mask_parms parms;

        memset(&parms.orvals, 0, sizeof(parms.orvals));
        memset(&parms.andvals, 0xff, sizeof(parms.andvals));
        parms.orvals[cr] = 1 << bit;
        on_each_cpu(smp_ctl_bit_callback, &parms, 0, 1);
}
EXPORT_SYMBOL(smp_ctl_set_bit);

/*
 * Clear a bit in a control register of all cpus
 */
void smp_ctl_clear_bit(int cr, int bit)
{
        struct ec_creg_mask_parms parms;

        memset(&parms.orvals, 0, sizeof(parms.orvals));
        memset(&parms.andvals, 0xff, sizeof(parms.andvals));
        parms.andvals[cr] = ~(1L << bit);
        on_each_cpu(smp_ctl_bit_callback, &parms, 0, 1);
}
EXPORT_SYMBOL(smp_ctl_clear_bit);

#if defined(CONFIG_ZFCPDUMP) || defined(CONFIG_ZFCPDUMP_MODULE)

/*
 * zfcpdump_prefix_array holds prefix registers for the following scenario:
 * 64 bit zfcpdump kernel and 31 bit kernel which is to be dumped. We have to
 * save its prefix registers, since they get lost, when switching from 31 bit
 * to 64 bit.
 */
unsigned int zfcpdump_prefix_array[NR_CPUS + 1] \
        __attribute__((__section__(".data")));

static void __init smp_get_save_areas(void)
{
        unsigned int cpu, cpu_num, rc;
        __u16 boot_cpu_addr;

        if (ipl_info.type != IPL_TYPE_FCP_DUMP)
                return;
        boot_cpu_addr = S390_lowcore.cpu_data.cpu_addr;
        cpu_num = 1;
        for (cpu = 0; cpu <= 65535; cpu++) {
                if ((u16) cpu == boot_cpu_addr)
                        continue;
                __cpu_logical_map[1] = (__u16) cpu;
                if (signal_processor(1, sigp_sense) == sigp_not_operational)
                        continue;
                if (cpu_num >= NR_CPUS) {
                        printk("WARNING: Registers for cpu %i are not "
                               "saved, since dump kernel was compiled with"
                               "NR_CPUS=%i!\n", cpu_num, NR_CPUS);
                        continue;
                }
                zfcpdump_save_areas[cpu_num] =
                        alloc_bootmem(sizeof(union save_area));
                while (1) {
                        rc = signal_processor(1, sigp_stop_and_store_status);
                        if (rc != sigp_busy)
                                break;
                        cpu_relax();
                }
                memcpy(zfcpdump_save_areas[cpu_num],
                       (void *)(unsigned long) store_prefix() +
                       SAVE_AREA_BASE, SAVE_AREA_SIZE);
#ifdef __s390x__
                /* copy original prefix register */
                zfcpdump_save_areas[cpu_num]->s390x.pref_reg =
                        zfcpdump_prefix_array[cpu_num];
#endif
                cpu_num++;
        }
}

union save_area *zfcpdump_save_areas[NR_CPUS + 1];
EXPORT_SYMBOL_GPL(zfcpdump_save_areas);

#else
#define smp_get_save_areas() do { } while (0)
#endif

/*
 * Lets check how many CPUs we have.
 */

static unsigned int __init smp_count_cpus(void)
{
        unsigned int cpu, num_cpus;
        __u16 boot_cpu_addr;

        /*
         * cpu 0 is the boot cpu. See smp_prepare_boot_cpu.
         */

        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)
                        continue;
                __cpu_logical_map[1] = (__u16) cpu;
                if (signal_processor(1, sigp_sense) == sigp_not_operational)
                        continue;
                num_cpus++;
        }

        printk("Detected %d CPU's\n", (int) num_cpus);
        printk("Boot cpu address %2X\n", boot_cpu_addr);

        return num_cpus;
}

/*
 *      Activate a secondary processor.
 */
int __devinit start_secondary(void *cpuvoid)
{
        /* Setup the cpu */
        cpu_init();
        preempt_disable();
        /* Enable TOD clock interrupts on the secondary cpu. */
        init_cpu_timer();
#ifdef CONFIG_VIRT_TIMER
        /* Enable cpu timer interrupts on the secondary cpu. */
        init_cpu_vtimer();
#endif
        /* Enable pfault pseudo page faults on this cpu. */
        pfault_init();

        /* Mark this cpu as online */
        cpu_set(smp_processor_id(), cpu_online_map);
        /* Switch on interrupts */
        local_irq_enable();
        /* Print info about this processor */
        print_cpu_info(&S390_lowcore.cpu_data);
        /* cpu_idle will call schedule for us */
        cpu_idle();
        return 0;
}

static void __init smp_create_idle(unsigned int cpu)
{
        struct task_struct *p;

        /*
         *  don't care about the psw and regs settings since we'll never
         *  reschedule the forked task.
         */
        p = fork_idle(cpu);
        if (IS_ERR(p))
                panic("failed fork for CPU %u: %li", cpu, PTR_ERR(p));
        current_set[cpu] = p;
}

static int cpu_stopped(int cpu)
{
        __u32 status;

        /* Check for stopped state */
        if (signal_processor_ps(&status, 0, cpu, sigp_sense) ==
            sigp_status_stored) {
                if (status & 0x40)
                        return 1;
        }
        return 0;
}

/* Upping and downing of CPUs */

int __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;

        ccode = signal_processor_p((__u32)(unsigned long)(lowcore_ptr[cpu]),
                                   cpu, sigp_set_prefix);
        if (ccode) {
                printk("sigp_set_prefix failed for cpu %d "
                       "with condition code %d\n",
                       (int) cpu, (int) ccode);
                return -EIO;
        }

        idle = current_set[cpu];
        cpu_lowcore = lowcore_ptr[cpu];
        cpu_lowcore->kernel_stack = (unsigned long)
                task_stack_page(idle) + THREAD_SIZE;
        sf = (struct stack_frame *) (cpu_lowcore->kernel_stack
                                     - sizeof(struct pt_regs)
                                     - sizeof(struct stack_frame));
        memset(sf, 0, sizeof(struct stack_frame));
        sf->gprs[9] = (unsigned long) sf;
        cpu_lowcore->save_area[15] = (unsigned long) sf;
        __ctl_store(cpu_lowcore->cregs_save_area[0], 0, 15);
        asm volatile(
                "       stam    0,15,0(%0)"
                : : "a" (&cpu_lowcore->access_regs_save_area) : "memory");
        cpu_lowcore->percpu_offset = __per_cpu_offset[cpu];
        cpu_lowcore->current_task = (unsigned long) idle;
        cpu_lowcore->cpu_data.cpu_nr = cpu;
        eieio();

        while (signal_processor(cpu, sigp_restart) == sigp_busy)
                udelay(10);

        while (!cpu_online(cpu))
                cpu_relax();
        return 0;
}

static unsigned int __initdata additional_cpus;
static unsigned int __initdata possible_cpus;

void __init smp_setup_cpu_possible_map(void)
{
        unsigned int phy_cpus, pos_cpus, cpu;

        smp_get_save_areas();
        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);

        for (cpu = 0; cpu < pos_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);

int __cpu_disable(void)
{
        struct ec_creg_mask_parms cr_parms;
        int cpu = smp_processor_id();

        cpu_clear(cpu, cpu_online_map);

        /* Disable pfault pseudo page faults on this cpu. */
        pfault_fini();

        memset(&cr_parms.orvals, 0, sizeof(cr_parms.orvals));
        memset(&cr_parms.andvals, 0xff, sizeof(cr_parms.andvals));

        /* disable all external interrupts */
        cr_parms.orvals[0] = 0;
        cr_parms.andvals[0] = ~(1 << 15 | 1 << 14 | 1 << 13 | 1 << 12 |
                                1 << 11 | 1 << 10 | 1 <<  6 | 1 <<  4);
        /* disable all I/O interrupts */
        cr_parms.orvals[6] = 0;
        cr_parms.andvals[6] = ~(1 << 31 | 1 << 30 | 1 << 29 | 1 << 28 |
                                1 << 27 | 1 << 26 | 1 << 25 | 1 << 24);
        /* disable most machine checks */
        cr_parms.orvals[14] = 0;
        cr_parms.andvals[14] = ~(1 << 28 | 1 << 27 | 1 << 26 |
                                 1 << 25 | 1 << 24);

        smp_ctl_bit_callback(&cr_parms);

        return 0;
}

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);
}

void cpu_die(void)
{
        idle_task_exit();
        signal_processor(smp_processor_id(), sigp_stop);
        BUG();
        for (;;);
}

#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;

        /* 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);

        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 */
#endif
        set_prefix((u32)(unsigned long) lowcore_ptr[smp_processor_id()]);

        for_each_possible_cpu(cpu)
                if (cpu != smp_processor_id())
                        smp_create_idle(cpu);
}

void __devinit smp_prepare_boot_cpu(void)
{
        BUG_ON(smp_processor_id() != 0);

        cpu_set(0, cpu_online_map);
        S390_lowcore.percpu_offset = __per_cpu_offset[0];
        current_set[0] = current;
}

void smp_cpus_done(unsigned int max_cpus)
{
        cpu_present_map = cpu_possible_map;
}

/*
 * the frequency of the profiling timer can be changed
 * by writing a multiplier value into /proc/profile.
 *
 * usually you want to run this on all CPUs ;)
 */
int setup_profiling_timer(unsigned int multiplier)
{
        return 0;
}

static DEFINE_PER_CPU(struct cpu, cpu_devices);

static ssize_t show_capability(struct sys_device *dev, char *buf)
{
        unsigned int capability;
        int rc;

        rc = get_cpu_capability(&capability);
        if (rc)
                return rc;
        return sprintf(buf, "%u\n", capability);
}
static SYSDEV_ATTR(capability, 0444, show_capability, NULL);

static int __cpuinit smp_cpu_notify(struct notifier_block *self,
                                    unsigned long action, void *hcpu)
{
        unsigned int cpu = (unsigned int)(long)hcpu;
        struct cpu *c = &per_cpu(cpu_devices, cpu);
        struct sys_device *s = &c->sysdev;

        switch (action) {
        case CPU_ONLINE:
                if (sysdev_create_file(s, &attr_capability))
                        return NOTIFY_BAD;
                break;
        case CPU_DEAD:
                sysdev_remove_file(s, &attr_capability);
                break;
        }
        return NOTIFY_OK;
}

static struct notifier_block __cpuinitdata smp_cpu_nb = {
        .notifier_call = smp_cpu_notify,
};

static int __init topology_init(void)
{
        int cpu;

        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;
                sysdev_create_file(s, &attr_capability);
        }
        return 0;
}
subsys_initcall(topology_init);