smp.c

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/*
 *  SMP related functions
 *
 *    Copyright IBM Corp. 1999, 2012
 *    Author(s): Denis Joseph Barrow,
 *       Martin Schwidefsky <[email protected]>,
 *       Heiko Carstens <[email protected]>,
 *
 *  based on other smp stuff by
 *    (c) 1995 Alan Cox, CymruNET Ltd  <[email protected]>
 *    (c) 1998 Ingo Molnar
 *
 * The code outside of smp.c uses logical cpu numbers, only smp.c does
 * the translation of logical to physical cpu ids. All new code that
 * operates on physical cpu numbers needs to go into smp.c.
 */

#define KMSG_COMPONENT "cpu"
#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt

#include <linux/workqueue.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/err.h>
#include <linux/spinlock.h>
#include <linux/kernel_stat.h>
#include <linux/delay.h>
#include <linux/interrupt.h>
#include <linux/irqflags.h>
#include <linux/cpu.h>
#include <linux/slab.h>
#include <linux/crash_dump.h>
#include <asm/asm-offsets.h>
#include <asm/switch_to.h>
#include <asm/facility.h>
#include <asm/ipl.h>
#include <asm/setup.h>
#include <asm/irq.h>
#include <asm/tlbflush.h>
#include <asm/vtimer.h>
#include <asm/lowcore.h>
#include <asm/sclp.h>
#include <asm/vdso.h>
#include <asm/debug.h>
#include <asm/os_info.h>
#include <asm/sigp.h>
#include "entry.h"

enum {
    ec_schedule = 0,
    ec_call_function,
    ec_call_function_single,
    ec_stop_cpu,
};

enum {
    CPU_STATE_STANDBY,
    CPU_STATE_CONFIGURED,
};

struct pcpu {
    struct cpu cpu;
    struct _lowcore *lowcore;   /* lowcore page(s) for the cpu */
    unsigned long async_stack;  /* async stack for the cpu */
    unsigned long panic_stack;  /* panic stack for the cpu */
    unsigned long ec_mask;      /* bit mask for ec_xxx functions */
    int state;          /* physical cpu state */
    int polarization;       /* physical polarization */
    u16 address;            /* physical cpu address */
};

static u8 boot_cpu_type;
static u16 boot_cpu_address;
static struct pcpu pcpu_devices[NR_CPUS];

/*
 * The smp_cpu_state_mutex must be held when changing the state or polarization
 * member of a pcpu data structure within the pcpu_devices arreay.
 */
DEFINE_MUTEX(smp_cpu_state_mutex);

/*
 * Signal processor helper functions.
 */
static inline int __pcpu_sigp(u16 addr, u8 order, u32 parm, u32 *status)
{
    register unsigned int reg1 asm ("1") = parm;
    int cc;

    asm volatile(
        "   sigp    %1,%2,0(%3)\n"
        "   ipm %0\n"
        "   srl %0,28\n"
        : "=d" (cc), "+d" (reg1) : "d" (addr), "a" (order) : "cc");
    if (status && cc == 1)
        *status = reg1;
    return cc;
}

static inline int __pcpu_sigp_relax(u16 addr, u8 order, u32 parm, u32 *status)
{
    int cc;

    while (1) {
        cc = __pcpu_sigp(addr, order, parm, NULL);
        if (cc != SIGP_CC_BUSY)
            return cc;
        cpu_relax();
    }
}

static int pcpu_sigp_retry(struct pcpu *pcpu, u8 order, u32 parm)
{
    int cc, retry;

    for (retry = 0; ; retry++) {
        cc = __pcpu_sigp(pcpu->address, order, parm, NULL);
        if (cc != SIGP_CC_BUSY)
            break;
        if (retry >= 3)
            udelay(10);
    }
    return cc;
}

static inline int pcpu_stopped(struct pcpu *pcpu)
{
    u32 uninitialized_var(status);

    if (__pcpu_sigp(pcpu->address, SIGP_SENSE,
            0, &status) != SIGP_CC_STATUS_STORED)
        return 0;
    return !!(status & (SIGP_STATUS_CHECK_STOP|SIGP_STATUS_STOPPED));
}

static inline int pcpu_running(struct pcpu *pcpu)
{
    if (__pcpu_sigp(pcpu->address, SIGP_SENSE_RUNNING,
            0, NULL) != SIGP_CC_STATUS_STORED)
        return 1;
    /* Status stored condition code is equivalent to cpu not running. */
    return 0;
}

/*
 * Find struct pcpu by cpu address.
 */
static struct pcpu *pcpu_find_address(const struct cpumask *mask, int address)
{
    int cpu;

    for_each_cpu(cpu, mask)
        if (pcpu_devices[cpu].address == address)
            return pcpu_devices + cpu;
    return NULL;
}

static void pcpu_ec_call(struct pcpu *pcpu, int ec_bit)
{
    int order;

    set_bit(ec_bit, &pcpu->ec_mask);
    order = pcpu_running(pcpu) ?
        SIGP_EXTERNAL_CALL : SIGP_EMERGENCY_SIGNAL;
    pcpu_sigp_retry(pcpu, order, 0);
}

static int __cpuinit pcpu_alloc_lowcore(struct pcpu *pcpu, int cpu)
{
    struct _lowcore *lc;

    if (pcpu != &pcpu_devices[0]) {
        pcpu->lowcore = (struct _lowcore *)
            __get_free_pages(GFP_KERNEL | GFP_DMA, LC_ORDER);
        pcpu->async_stack = __get_free_pages(GFP_KERNEL, ASYNC_ORDER);
        pcpu->panic_stack = __get_free_page(GFP_KERNEL);
        if (!pcpu->lowcore || !pcpu->panic_stack || !pcpu->async_stack)
            goto out;
    }
    lc = pcpu->lowcore;
    memcpy(lc, &S390_lowcore, 512);
    memset((char *) lc + 512, 0, sizeof(*lc) - 512);
    lc->async_stack = pcpu->async_stack + ASYNC_SIZE;
    lc->panic_stack = pcpu->panic_stack + PAGE_SIZE;
    lc->cpu_nr = cpu;
#ifndef CONFIG_64BIT
    if (MACHINE_HAS_IEEE) {
        lc->extended_save_area_addr = get_zeroed_page(GFP_KERNEL);
        if (!lc->extended_save_area_addr)
            goto out;
    }
#else
    if (vdso_alloc_per_cpu(lc))
        goto out;
#endif
    lowcore_ptr[cpu] = lc;
    pcpu_sigp_retry(pcpu, SIGP_SET_PREFIX, (u32)(unsigned long) lc);
    return 0;
out:
    if (pcpu != &pcpu_devices[0]) {
        free_page(pcpu->panic_stack);
        free_pages(pcpu->async_stack, ASYNC_ORDER);
        free_pages((unsigned long) pcpu->lowcore, LC_ORDER);
    }
    return -ENOMEM;
}

#ifdef CONFIG_HOTPLUG_CPU

static void pcpu_free_lowcore(struct pcpu *pcpu)
{
    pcpu_sigp_retry(pcpu, SIGP_SET_PREFIX, 0);
    lowcore_ptr[pcpu - pcpu_devices] = NULL;
#ifndef CONFIG_64BIT
    if (MACHINE_HAS_IEEE) {
        struct _lowcore *lc = pcpu->lowcore;

        free_page((unsigned long) lc->extended_save_area_addr);
        lc->extended_save_area_addr = 0;
    }
#else
    vdso_free_per_cpu(pcpu->lowcore);
#endif
    if (pcpu != &pcpu_devices[0]) {
        free_page(pcpu->panic_stack);
        free_pages(pcpu->async_stack, ASYNC_ORDER);
        free_pages((unsigned long) pcpu->lowcore, LC_ORDER);
    }
}

#endif /* CONFIG_HOTPLUG_CPU */

static void pcpu_prepare_secondary(struct pcpu *pcpu, int cpu)
{
    struct _lowcore *lc = pcpu->lowcore;

    atomic_inc(&init_mm.context.attach_count);
    lc->cpu_nr = cpu;
    lc->percpu_offset = __per_cpu_offset[cpu];
    lc->kernel_asce = S390_lowcore.kernel_asce;
    lc->machine_flags = S390_lowcore.machine_flags;
    lc->ftrace_func = S390_lowcore.ftrace_func;
    lc->user_timer = lc->system_timer = lc->steal_timer = 0;
    __ctl_store(lc->cregs_save_area, 0, 15);
    save_access_regs((unsigned int *) lc->access_regs_save_area);
    memcpy(lc->stfle_fac_list, S390_lowcore.stfle_fac_list,
           MAX_FACILITY_BIT/8);
}

static void pcpu_attach_task(struct pcpu *pcpu, struct task_struct *tsk)
{
    struct _lowcore *lc = pcpu->lowcore;
    struct thread_info *ti = task_thread_info(tsk);

    lc->kernel_stack = (unsigned long) task_stack_page(tsk) + THREAD_SIZE;
    lc->thread_info = (unsigned long) task_thread_info(tsk);
    lc->current_task = (unsigned long) tsk;
    lc->user_timer = ti->user_timer;
    lc->system_timer = ti->system_timer;
    lc->steal_timer = 0;
}

static void pcpu_start_fn(struct pcpu *pcpu, void (*func)(void *), void *data)
{
    struct _lowcore *lc = pcpu->lowcore;

    lc->restart_stack = lc->kernel_stack;
    lc->restart_fn = (unsigned long) func;
    lc->restart_data = (unsigned long) data;
    lc->restart_source = -1UL;
    pcpu_sigp_retry(pcpu, SIGP_RESTART, 0);
}

/*
 * Call function via PSW restart on pcpu and stop the current cpu.
 */
static void pcpu_delegate(struct pcpu *pcpu, void (*func)(void *),
              void *data, unsigned long stack)
{
    struct _lowcore *lc = lowcore_ptr[pcpu - pcpu_devices];
    unsigned long source_cpu = stap();

    __load_psw_mask(psw_kernel_bits);
    if (pcpu->address == source_cpu)
        func(data); /* should not return */
    /* Stop target cpu (if func returns this stops the current cpu). */
    pcpu_sigp_retry(pcpu, SIGP_STOP, 0);
    /* Restart func on the target cpu and stop the current cpu. */
    mem_assign_absolute(lc->restart_stack, stack);
    mem_assign_absolute(lc->restart_fn, (unsigned long) func);
    mem_assign_absolute(lc->restart_data, (unsigned long) data);
    mem_assign_absolute(lc->restart_source, source_cpu);
    asm volatile(
        "0: sigp    0,%0,%2 # sigp restart to target cpu\n"
        "   brc 2,0b    # busy, try again\n"
        "1: sigp    0,%1,%3 # sigp stop to current cpu\n"
        "   brc 2,1b    # busy, try again\n"
        : : "d" (pcpu->address), "d" (source_cpu),
            "K" (SIGP_RESTART), "K" (SIGP_STOP)
        : "0", "1", "cc");
    for (;;) ;
}

/*
 * Call function on an online CPU.
 */
void smp_call_online_cpu(void (*func)(void *), void *data)
{
    struct pcpu *pcpu;

    /* Use the current cpu if it is online. */
    pcpu = pcpu_find_address(cpu_online_mask, stap());
    if (!pcpu)
        /* Use the first online cpu. */
        pcpu = pcpu_devices + cpumask_first(cpu_online_mask);
    pcpu_delegate(pcpu, func, data, (unsigned long) restart_stack);
}

/*
 * Call function on the ipl CPU.
 */
void smp_call_ipl_cpu(void (*func)(void *), void *data)
{
    pcpu_delegate(&pcpu_devices[0], func, data,
              pcpu_devices->panic_stack + PAGE_SIZE);
}

int smp_find_processor_id(u16 address)
{
    int cpu;

    for_each_present_cpu(cpu)
        if (pcpu_devices[cpu].address == address)
            return cpu;
    return -1;
}

int smp_vcpu_scheduled(int cpu)
{
    return pcpu_running(pcpu_devices + cpu);
}

void smp_yield(void)
{
    if (MACHINE_HAS_DIAG44)
        asm volatile("diag 0,0,0x44");
}

void smp_yield_cpu(int cpu)
{
    if (MACHINE_HAS_DIAG9C)
        asm volatile("diag %0,0,0x9c"
                 : : "d" (pcpu_devices[cpu].address));
    else if (MACHINE_HAS_DIAG44)
        asm volatile("diag 0,0,0x44");
}

/*
 * Send cpus emergency shutdown signal. This gives the cpus the
 * opportunity to complete outstanding interrupts.
 */
void smp_emergency_stop(cpumask_t *cpumask)
{
    u64 end;
    int cpu;

    end = get_clock() + (1000000UL << 12);
    for_each_cpu(cpu, cpumask) {
        struct pcpu *pcpu = pcpu_devices + cpu;
        set_bit(ec_stop_cpu, &pcpu->ec_mask);
        while (__pcpu_sigp(pcpu->address, SIGP_EMERGENCY_SIGNAL,
                   0, NULL) == SIGP_CC_BUSY &&
               get_clock() < end)
            cpu_relax();
    }
    while (get_clock() < end) {
        for_each_cpu(cpu, cpumask)
            if (pcpu_stopped(pcpu_devices + cpu))
                cpumask_clear_cpu(cpu, cpumask);
        if (cpumask_empty(cpumask))
            break;
        cpu_relax();
    }
}

/*
 * Stop all cpus but the current one.
 */
void smp_send_stop(void)
{
    cpumask_t cpumask;
    int cpu;

    /* Disable all interrupts/machine checks */
    __load_psw_mask(psw_kernel_bits | PSW_MASK_DAT);
    trace_hardirqs_off();

    debug_set_critical();
    cpumask_copy(&cpumask, cpu_online_mask);
    cpumask_clear_cpu(smp_processor_id(), &cpumask);

    if (oops_in_progress)
        smp_emergency_stop(&cpumask);

    /* stop all processors */
    for_each_cpu(cpu, &cpumask) {
        struct pcpu *pcpu = pcpu_devices + cpu;
        pcpu_sigp_retry(pcpu, SIGP_STOP, 0);
        while (!pcpu_stopped(pcpu))
            cpu_relax();
    }
}

/*
 * Stop the current cpu.
 */
void smp_stop_cpu(void)
{
    pcpu_sigp_retry(pcpu_devices + smp_processor_id(), SIGP_STOP, 0);
    for (;;) ;
}

/*
 * This is the main routine where commands issued by other
 * cpus are handled.
 */
static void do_ext_call_interrupt(struct ext_code ext_code,
                  unsigned int param32, unsigned long param64)
{
    unsigned long bits;
    int cpu;

    cpu = smp_processor_id();
    if (ext_code.code == 0x1202)
        kstat_cpu(cpu).irqs[EXTINT_EXC]++;
    else
        kstat_cpu(cpu).irqs[EXTINT_EMS]++;
    /*
     * handle bit signal external calls
     */
    bits = xchg(&pcpu_devices[cpu].ec_mask, 0);

    if (test_bit(ec_stop_cpu, &bits))
        smp_stop_cpu();

    if (test_bit(ec_schedule, &bits))
        scheduler_ipi();

    if (test_bit(ec_call_function, &bits))
        generic_smp_call_function_interrupt();

    if (test_bit(ec_call_function_single, &bits))
        generic_smp_call_function_single_interrupt();

}

void arch_send_call_function_ipi_mask(const struct cpumask *mask)
{
    int cpu;

    for_each_cpu(cpu, mask)
        pcpu_ec_call(pcpu_devices + cpu, ec_call_function);
}

void arch_send_call_function_single_ipi(int cpu)
{
    pcpu_ec_call(pcpu_devices + cpu, ec_call_function_single);
}

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

void smp_ptlb_all(void)
{
    on_each_cpu(smp_ptlb_callback, NULL, 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)
{
    pcpu_ec_call(pcpu_devices + cpu, ec_schedule);
}

/*
 * parameter area for the set/clear control bit callbacks
 */
struct ec_creg_mask_parms {
    unsigned long orval;
    unsigned long andval;
    int cr;
};

/*
 * 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];

    __ctl_store(cregs, 0, 15);
    cregs[pp->cr] = (cregs[pp->cr] & pp->andval) | pp->orval;
    __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 = { 1UL << bit, -1UL, cr };

    on_each_cpu(smp_ctl_bit_callback, &parms, 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 = { 0, ~(1UL << bit), cr };

    on_each_cpu(smp_ctl_bit_callback, &parms, 1);
}
EXPORT_SYMBOL(smp_ctl_clear_bit);

#if defined(CONFIG_ZFCPDUMP) || defined(CONFIG_CRASH_DUMP)

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

static void __init smp_get_save_area(int cpu, u16 address)
{
    void *lc = pcpu_devices[0].lowcore;
    struct save_area *save_area;

    if (is_kdump_kernel())
        return;
    if (!OLDMEM_BASE && (address == boot_cpu_address ||
                 ipl_info.type != IPL_TYPE_FCP_DUMP))
        return;
    if (cpu >= NR_CPUS) {
        pr_warning("CPU %i exceeds the maximum %i and is excluded "
               "from the dump\n", cpu, NR_CPUS - 1);
        return;
    }
    save_area = kmalloc(sizeof(struct save_area), GFP_KERNEL);
    if (!save_area)
        panic("could not allocate memory for save area\n");
    zfcpdump_save_areas[cpu] = save_area;
#ifdef CONFIG_CRASH_DUMP
    if (address == boot_cpu_address) {
        /* Copy the registers of the boot cpu. */
        copy_oldmem_page(1, (void *) save_area, sizeof(*save_area),
                 SAVE_AREA_BASE - PAGE_SIZE, 0);
        return;
    }
#endif
    /* Get the registers of a non-boot cpu. */
    __pcpu_sigp_relax(address, SIGP_STOP_AND_STORE_STATUS, 0, NULL);
    memcpy_real(save_area, lc + SAVE_AREA_BASE, sizeof(*save_area));
}

int smp_store_status(int cpu)
{
    struct pcpu *pcpu;

    pcpu = pcpu_devices + cpu;
    if (__pcpu_sigp_relax(pcpu->address, SIGP_STOP_AND_STORE_STATUS,
                  0, NULL) != SIGP_CC_ORDER_CODE_ACCEPTED)
        return -EIO;
    return 0;
}

#else /* CONFIG_ZFCPDUMP || CONFIG_CRASH_DUMP */

static inline void smp_get_save_area(int cpu, u16 address) { }

#endif /* CONFIG_ZFCPDUMP || CONFIG_CRASH_DUMP */

void smp_cpu_set_polarization(int cpu, int val)
{
    pcpu_devices[cpu].polarization = val;
}

int smp_cpu_get_polarization(int cpu)
{
    return pcpu_devices[cpu].polarization;
}

static struct sclp_cpu_info *smp_get_cpu_info(void)
{
    static int use_sigp_detection;
    struct sclp_cpu_info *info;
    int address;

    info = kzalloc(sizeof(*info), GFP_KERNEL);
    if (info && (use_sigp_detection || sclp_get_cpu_info(info))) {
        use_sigp_detection = 1;
        for (address = 0; address <= MAX_CPU_ADDRESS; address++) {
            if (__pcpu_sigp_relax(address, SIGP_SENSE, 0, NULL) ==
                SIGP_CC_NOT_OPERATIONAL)
                continue;
            info->cpu[info->configured].address = address;
            info->configured++;
        }
        info->combined = info->configured;
    }
    return info;
}

static int __devinit smp_add_present_cpu(int cpu);

static int __devinit __smp_rescan_cpus(struct sclp_cpu_info *info,
                       int sysfs_add)
{
    struct pcpu *pcpu;
    cpumask_t avail;
    int cpu, nr, i;

    nr = 0;
    cpumask_xor(&avail, cpu_possible_mask, cpu_present_mask);
    cpu = cpumask_first(&avail);
    for (i = 0; (i < info->combined) && (cpu < nr_cpu_ids); i++) {
        if (info->has_cpu_type && info->cpu[i].type != boot_cpu_type)
            continue;
        if (pcpu_find_address(cpu_present_mask, info->cpu[i].address))
            continue;
        pcpu = pcpu_devices + cpu;
        pcpu->address = info->cpu[i].address;
        pcpu->state = (cpu >= info->configured) ?
            CPU_STATE_STANDBY : CPU_STATE_CONFIGURED;
        smp_cpu_set_polarization(cpu, POLARIZATION_UNKNOWN);
        set_cpu_present(cpu, true);
        if (sysfs_add && smp_add_present_cpu(cpu) != 0)
            set_cpu_present(cpu, false);
        else
            nr++;
        cpu = cpumask_next(cpu, &avail);
    }
    return nr;
}

static void __init smp_detect_cpus(void)
{
    unsigned int cpu, c_cpus, s_cpus;
    struct sclp_cpu_info *info;

    info = smp_get_cpu_info();
    if (!info)
        panic("smp_detect_cpus failed to allocate memory\n");
    if (info->has_cpu_type) {
        for (cpu = 0; cpu < info->combined; cpu++) {
            if (info->cpu[cpu].address != boot_cpu_address)
                continue;
            /* The boot cpu dictates the cpu type. */
            boot_cpu_type = info->cpu[cpu].type;
            break;
        }
    }
    c_cpus = s_cpus = 0;
    for (cpu = 0; cpu < info->combined; cpu++) {
        if (info->has_cpu_type && info->cpu[cpu].type != boot_cpu_type)
            continue;
        if (cpu < info->configured) {
            smp_get_save_area(c_cpus, info->cpu[cpu].address);
            c_cpus++;
        } else
            s_cpus++;
    }
    pr_info("%d configured CPUs, %d standby CPUs\n", c_cpus, s_cpus);
    get_online_cpus();
    __smp_rescan_cpus(info, 0);
    put_online_cpus();
    kfree(info);
}

/*
 *  Activate a secondary processor.
 */
static void __cpuinit smp_start_secondary(void *cpuvoid)
{
    S390_lowcore.last_update_clock = get_clock();
    S390_lowcore.restart_stack = (unsigned long) restart_stack;
    S390_lowcore.restart_fn = (unsigned long) do_restart;
    S390_lowcore.restart_data = 0;
    S390_lowcore.restart_source = -1UL;
    restore_access_regs(S390_lowcore.access_regs_save_area);
    __ctl_load(S390_lowcore.cregs_save_area, 0, 15);
    __load_psw_mask(psw_kernel_bits | PSW_MASK_DAT);
    cpu_init();
    preempt_disable();
    init_cpu_timer();
    init_cpu_vtimer();
    pfault_init();
    notify_cpu_starting(smp_processor_id());
    set_cpu_online(smp_processor_id(), true);
    local_irq_enable();
    /* cpu_idle will call schedule for us */
    cpu_idle();
}

/* Upping and downing of CPUs */
int __cpuinit __cpu_up(unsigned int cpu, struct task_struct *tidle)
{
    struct pcpu *pcpu;
    int rc;

    pcpu = pcpu_devices + cpu;
    if (pcpu->state != CPU_STATE_CONFIGURED)
        return -EIO;
    if (pcpu_sigp_retry(pcpu, SIGP_INITIAL_CPU_RESET, 0) !=
        SIGP_CC_ORDER_CODE_ACCEPTED)
        return -EIO;

    rc = pcpu_alloc_lowcore(pcpu, cpu);
    if (rc)
        return rc;
    pcpu_prepare_secondary(pcpu, cpu);
    pcpu_attach_task(pcpu, tidle);
    pcpu_start_fn(pcpu, smp_start_secondary, NULL);
    while (!cpu_online(cpu))
        cpu_relax();
    return 0;
}

static int __init setup_possible_cpus(char *s)
{
    int max, cpu;

    if (kstrtoint(s, 0, &max) < 0)
        return 0;
    init_cpu_possible(cpumask_of(0));
    for (cpu = 1; cpu < max && cpu < nr_cpu_ids; cpu++)
        set_cpu_possible(cpu, true);
    return 0;
}
early_param("possible_cpus", setup_possible_cpus);

#ifdef CONFIG_HOTPLUG_CPU

int __cpu_disable(void)
{
    unsigned long cregs[16];

    set_cpu_online(smp_processor_id(), false);
    /* Disable pseudo page faults on this cpu. */
    pfault_fini();
    /* Disable interrupt sources via control register. */
    __ctl_store(cregs, 0, 15);
    cregs[0]  &= ~0x0000ee70UL; /* disable all external interrupts */
    cregs[6]  &= ~0xff000000UL; /* disable all I/O interrupts */
    cregs[14] &= ~0x1f000000UL; /* disable most machine checks */
    __ctl_load(cregs, 0, 15);
    return 0;
}

void __cpu_die(unsigned int cpu)
{
    struct pcpu *pcpu;

    /* Wait until target cpu is down */
    pcpu = pcpu_devices + cpu;
    while (!pcpu_stopped(pcpu))
        cpu_relax();
    pcpu_free_lowcore(pcpu);
    atomic_dec(&init_mm.context.attach_count);
}

void __noreturn cpu_die(void)
{
    idle_task_exit();
    pcpu_sigp_retry(pcpu_devices + smp_processor_id(), SIGP_STOP, 0);
    for (;;) ;
}

#endif /* CONFIG_HOTPLUG_CPU */

void __init smp_prepare_cpus(unsigned int max_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");
    /* request the 0x1202 external call external interrupt */
    if (register_external_interrupt(0x1202, do_ext_call_interrupt) != 0)
        panic("Couldn't request external interrupt 0x1202");
    smp_detect_cpus();
}

void __init smp_prepare_boot_cpu(void)
{
    struct pcpu *pcpu = pcpu_devices;

    boot_cpu_address = stap();
    pcpu->state = CPU_STATE_CONFIGURED;
    pcpu->address = boot_cpu_address;
    pcpu->lowcore = (struct _lowcore *)(unsigned long) store_prefix();
    pcpu->async_stack = S390_lowcore.async_stack - ASYNC_SIZE;
    pcpu->panic_stack = S390_lowcore.panic_stack - PAGE_SIZE;
    S390_lowcore.percpu_offset = __per_cpu_offset[0];
    smp_cpu_set_polarization(0, POLARIZATION_UNKNOWN);
    set_cpu_present(0, true);
    set_cpu_online(0, true);
}

void __init smp_cpus_done(unsigned int max_cpus)
{
}

void __init smp_setup_processor_id(void)
{
    S390_lowcore.cpu_nr = 0;
}

/*
 * 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;
}

#ifdef CONFIG_HOTPLUG_CPU
static ssize_t cpu_configure_show(struct device *dev,
                  struct device_attribute *attr, char *buf)
{
    ssize_t count;

    mutex_lock(&smp_cpu_state_mutex);
    count = sprintf(buf, "%d\n", pcpu_devices[dev->id].state);
    mutex_unlock(&smp_cpu_state_mutex);
    return count;
}

static ssize_t cpu_configure_store(struct device *dev,
                   struct device_attribute *attr,
                   const char *buf, size_t count)
{
    struct pcpu *pcpu;
    int cpu, val, rc;
    char delim;

    if (sscanf(buf, "%d %c", &val, &delim) != 1)
        return -EINVAL;
    if (val != 0 && val != 1)
        return -EINVAL;
    get_online_cpus();
    mutex_lock(&smp_cpu_state_mutex);
    rc = -EBUSY;
    /* disallow configuration changes of online cpus and cpu 0 */
    cpu = dev->id;
    if (cpu_online(cpu) || cpu == 0)
        goto out;
    pcpu = pcpu_devices + cpu;
    rc = 0;
    switch (val) {
    case 0:
        if (pcpu->state != CPU_STATE_CONFIGURED)
            break;
        rc = sclp_cpu_deconfigure(pcpu->address);
        if (rc)
            break;
        pcpu->state = CPU_STATE_STANDBY;
        smp_cpu_set_polarization(cpu, POLARIZATION_UNKNOWN);
        topology_expect_change();
        break;
    case 1:
        if (pcpu->state != CPU_STATE_STANDBY)
            break;
        rc = sclp_cpu_configure(pcpu->address);
        if (rc)
            break;
        pcpu->state = CPU_STATE_CONFIGURED;
        smp_cpu_set_polarization(cpu, POLARIZATION_UNKNOWN);
        topology_expect_change();
        break;
    default:
        break;
    }
out:
    mutex_unlock(&smp_cpu_state_mutex);
    put_online_cpus();
    return rc ? rc : count;
}
static DEVICE_ATTR(configure, 0644, cpu_configure_show, cpu_configure_store);
#endif /* CONFIG_HOTPLUG_CPU */

static ssize_t show_cpu_address(struct device *dev,
                struct device_attribute *attr, char *buf)
{
    return sprintf(buf, "%d\n", pcpu_devices[dev->id].address);
}
static DEVICE_ATTR(address, 0444, show_cpu_address, NULL);

static struct attribute *cpu_common_attrs[] = {
#ifdef CONFIG_HOTPLUG_CPU
    &dev_attr_configure.attr,
#endif
    &dev_attr_address.attr,
    NULL,
};

static struct attribute_group cpu_common_attr_group = {
    .attrs = cpu_common_attrs,
};

static ssize_t show_idle_count(struct device *dev,
                struct device_attribute *attr, char *buf)
{
    struct s390_idle_data *idle = &per_cpu(s390_idle, dev->id);
    unsigned long long idle_count;
    unsigned int sequence;

    do {
        sequence = ACCESS_ONCE(idle->sequence);
        idle_count = ACCESS_ONCE(idle->idle_count);
        if (ACCESS_ONCE(idle->clock_idle_enter))
            idle_count++;
    } while ((sequence & 1) || (idle->sequence != sequence));
    return sprintf(buf, "%llu\n", idle_count);
}
static DEVICE_ATTR(idle_count, 0444, show_idle_count, NULL);

static ssize_t show_idle_time(struct device *dev,
                struct device_attribute *attr, char *buf)
{
    struct s390_idle_data *idle = &per_cpu(s390_idle, dev->id);
    unsigned long long now, idle_time, idle_enter, idle_exit;
    unsigned int sequence;

    do {
        now = get_clock();
        sequence = ACCESS_ONCE(idle->sequence);
        idle_time = ACCESS_ONCE(idle->idle_time);
        idle_enter = ACCESS_ONCE(idle->clock_idle_enter);
        idle_exit = ACCESS_ONCE(idle->clock_idle_exit);
    } while ((sequence & 1) || (idle->sequence != sequence));
    idle_time += idle_enter ? ((idle_exit ? : now) - idle_enter) : 0;
    return sprintf(buf, "%llu\n", idle_time >> 12);
}
static DEVICE_ATTR(idle_time_us, 0444, show_idle_time, NULL);

static struct attribute *cpu_online_attrs[] = {
    &dev_attr_idle_count.attr,
    &dev_attr_idle_time_us.attr,
    NULL,
};

static struct attribute_group cpu_online_attr_group = {
    .attrs = cpu_online_attrs,
};

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 = &pcpu_devices[cpu].cpu;
    struct device *s = &c->dev;
    int err = 0;

    switch (action & ~CPU_TASKS_FROZEN) {
    case CPU_ONLINE:
        err = sysfs_create_group(&s->kobj, &cpu_online_attr_group);
        break;
    case CPU_DEAD:
        sysfs_remove_group(&s->kobj, &cpu_online_attr_group);
        break;
    }
    return notifier_from_errno(err);
}

static int __devinit smp_add_present_cpu(int cpu)
{
    struct cpu *c = &pcpu_devices[cpu].cpu;
    struct device *s = &c->dev;
    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)) {
        rc = sysfs_create_group(&s->kobj, &cpu_online_attr_group);
        if (rc)
            goto out_online;
    }
    rc = topology_cpu_init(c);
    if (rc)
        goto out_topology;
    return 0;

out_topology:
    if (cpu_online(cpu))
        sysfs_remove_group(&s->kobj, &cpu_online_attr_group);
out_online:
    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

int __ref smp_rescan_cpus(void)
{
    struct sclp_cpu_info *info;
    int nr;

    info = smp_get_cpu_info();
    if (!info)
        return -ENOMEM;
    get_online_cpus();
    mutex_lock(&smp_cpu_state_mutex);
    nr = __smp_rescan_cpus(info, 1);
    mutex_unlock(&smp_cpu_state_mutex);
    put_online_cpus();
    kfree(info);
    if (nr)
        topology_schedule_update();
    return 0;
}

static ssize_t __ref rescan_store(struct device *dev,
                  struct device_attribute *attr,
                  const char *buf,
                  size_t count)
{
    int rc;

    rc = smp_rescan_cpus();
    return rc ? rc : count;
}
static DEVICE_ATTR(rescan, 0200, NULL, rescan_store);
#endif /* CONFIG_HOTPLUG_CPU */

static int __init s390_smp_init(void)
{
    int cpu, rc;

    hotcpu_notifier(smp_cpu_notify, 0);
#ifdef CONFIG_HOTPLUG_CPU
    rc = device_create_file(cpu_subsys.dev_root, &dev_attr_rescan);
    if (rc)
        return rc;
#endif
    for_each_present_cpu(cpu) {
        rc = smp_add_present_cpu(cpu);
        if (rc)
            return rc;
    }
    return 0;
}
subsys_initcall(s390_smp_init);