s390: Use generic idle thread allocation

[mirror_ubuntu-zesty-kernel.git] / arch / s390 / kernel / smp.c

/*
 *  SMP related functions
 *
 *    Copyright IBM Corp. 1999,2012
 *    Author(s): Denis Joseph Barrow,
 *               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
 *
 * 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/timer.h>
#include <asm/lowcore.h>
#include <asm/sclp.h>
#include <asm/vdso.h>
#include <asm/debug.h>
#include <asm/os_info.h>
#include "entry.h"

enum {
        sigp_sense = 1,
        sigp_external_call = 2,
        sigp_emergency_signal = 3,
        sigp_start = 4,
        sigp_stop = 5,
        sigp_restart = 6,
        sigp_stop_and_store_status = 9,
        sigp_initial_cpu_reset = 11,
        sigp_cpu_reset = 12,
        sigp_set_prefix = 13,
        sigp_store_status_at_address = 14,
        sigp_store_extended_status_at_address = 15,
        sigp_set_architecture = 18,
        sigp_conditional_emergency_signal = 19,
        sigp_sense_running = 21,
};

enum {
        sigp_order_code_accepted = 0,
        sigp_status_stored = 1,
        sigp_busy = 2,
        sigp_not_operational = 3,
};

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 */
        u32 status;                     /* last status received via sigp */
        u16 address;                    /* physical cpu address */
};

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

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, status);
                if (cc != sigp_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, &pcpu->status);
                if (cc != sigp_busy)
                        break;
                if (retry >= 3)
                        udelay(10);
        }
        return cc;
}

static inline int pcpu_stopped(struct pcpu *pcpu)
{
        if (__pcpu_sigp(pcpu->address, sigp_sense,
                        0, &pcpu->status) != sigp_status_stored)
                return 0;
        /* Check for stopped and check stop state */
        return !!(pcpu->status & 0x50);
}

static inline int pcpu_running(struct pcpu *pcpu)
{
        if (__pcpu_sigp(pcpu->address, sigp_sense_running,
                        0, &pcpu->status) != sigp_status_stored)
                return 1;
        /* Check for running status */
        return !(pcpu->status & 0x400);
}

/*
 * 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;
}

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);
        }
}

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 = pcpu->lowcore;
        unsigned short this_cpu;

        __load_psw_mask(psw_kernel_bits);
        this_cpu = stap();
        if (pcpu->address == this_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. */
        lc->restart_stack = stack;
        lc->restart_fn = (unsigned long) func;
        lc->restart_data = (unsigned long) data;
        lc->restart_source = (unsigned long) this_cpu;
        asm volatile(
                "0:     sigp    0,%0,6  # sigp restart to target cpu\n"
                "       brc     2,0b    # busy, try again\n"
                "1:     sigp    0,%1,5  # sigp stop to current cpu\n"
                "       brc     2,1b    # busy, try again\n"
                : : "d" (pcpu->address), "d" (this_cpu) : "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_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_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 */

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_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;
                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());
        ipi_call_lock();
        set_cpu_online(smp_processor_id(), true);
        ipi_call_unlock();
        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_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 */

static void smp_call_os_info_init_fn(void)
{
        int (*init_fn)(void);
        unsigned long size;

        init_fn = os_info_old_entry(OS_INFO_INIT_FN, &size);
        if (!init_fn)
                return;
        init_fn();
}

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_call_os_info_init_fn();
        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];
        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;
                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;
                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_capability(struct device *dev,
                                struct device_attribute *attr, char *buf)
{
        unsigned int capability;
        int rc;

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

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->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->idle_enter);
                idle_exit = ACCESS_ONCE(idle->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_capability.attr,
        &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;
        struct s390_idle_data *idle;
        int err = 0;

        switch (action) {
        case CPU_ONLINE:
        case CPU_ONLINE_FROZEN:
                idle = &per_cpu(s390_idle, cpu);
                memset(idle, 0, sizeof(struct s390_idle_data));
                err = sysfs_create_group(&s->kobj, &cpu_online_attr_group);
                break;
        case CPU_DEAD:
        case CPU_DEAD_FROZEN:
                sysfs_remove_group(&s->kobj, &cpu_online_attr_group);
                break;
        }
        return notifier_from_errno(err);
}

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

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;

        register_cpu_notifier(&smp_cpu_nb);
#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);