x86/speculation/mds: Fix documentation typo

[linux/fpc-iii.git] / arch / s390 / kernel / smp.c

// SPDX-License-Identifier: GPL-2.0
/*
 *  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/bootmem.h>
#include <linux/export.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/err.h>
#include <linux/spinlock.h>
#include <linux/kernel_stat.h>
#include <linux/kmemleak.h>
#include <linux/delay.h>
#include <linux/interrupt.h>
#include <linux/irqflags.h>
#include <linux/cpu.h>
#include <linux/slab.h>
#include <linux/sched/hotplug.h>
#include <linux/sched/task_stack.h>
#include <linux/crash_dump.h>
#include <linux/memblock.h>
#include <asm/asm-offsets.h>
#include <asm/diag.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 <asm/idle.h>
#include <asm/nmi.h>
#include <asm/topology.h>
#include "entry.h"

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

enum {
        CPU_STATE_STANDBY,
        CPU_STATE_CONFIGURED,
};

static DEFINE_PER_CPU(struct cpu *, cpu_device);

struct pcpu {
        struct lowcore *lowcore;        /* lowcore page(s) for the cpu */
        unsigned long ec_mask;          /* bit mask for ec_xxx functions */
        unsigned long ec_clk;           /* sigp timestamp for ec_xxx */
        signed char state;              /* physical cpu state */
        signed char polarization;       /* physical polarization */
        u16 address;                    /* physical cpu address */
};

static u8 boot_core_type;
static struct pcpu pcpu_devices[NR_CPUS];

static struct kmem_cache *pcpu_mcesa_cache;

unsigned int smp_cpu_mt_shift;
EXPORT_SYMBOL(smp_cpu_mt_shift);

unsigned int smp_cpu_mtid;
EXPORT_SYMBOL(smp_cpu_mtid);

#ifdef CONFIG_CRASH_DUMP
__vector128 __initdata boot_cpu_vector_save_area[__NUM_VXRS];
#endif

static unsigned int smp_max_threads __initdata = -1U;

static int __init early_nosmt(char *s)
{
        smp_max_threads = 1;
        return 0;
}
early_param("nosmt", early_nosmt);

static int __init early_smt(char *s)
{
        get_option(&s, &smp_max_threads);
        return 0;
}
early_param("smt", early_smt);

/*
 * 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_relax(u16 addr, u8 order, unsigned long parm)
{
        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, u16 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;

        if (test_and_set_bit(ec_bit, &pcpu->ec_mask))
                return;
        order = pcpu_running(pcpu) ? SIGP_EXTERNAL_CALL : SIGP_EMERGENCY_SIGNAL;
        pcpu->ec_clk = get_tod_clock_fast();
        pcpu_sigp_retry(pcpu, order, 0);
}

#define ASYNC_FRAME_OFFSET (ASYNC_SIZE - STACK_FRAME_OVERHEAD - __PT_SIZE)
#define PANIC_FRAME_OFFSET (PAGE_SIZE - STACK_FRAME_OVERHEAD - __PT_SIZE)

static int pcpu_alloc_lowcore(struct pcpu *pcpu, int cpu)
{
        unsigned long async_stack, panic_stack;
        unsigned long mcesa_origin, mcesa_bits;
        struct lowcore *lc;

        mcesa_origin = mcesa_bits = 0;
        if (pcpu != &pcpu_devices[0]) {
                pcpu->lowcore = (struct lowcore *)
                        __get_free_pages(GFP_KERNEL | GFP_DMA, LC_ORDER);
                async_stack = __get_free_pages(GFP_KERNEL, ASYNC_ORDER);
                panic_stack = __get_free_page(GFP_KERNEL);
                if (!pcpu->lowcore || !panic_stack || !async_stack)
                        goto out;
                if (MACHINE_HAS_VX || MACHINE_HAS_GS) {
                        mcesa_origin = (unsigned long)
                                kmem_cache_alloc(pcpu_mcesa_cache, GFP_KERNEL);
                        if (!mcesa_origin)
                                goto out;
                        /* The pointer is stored with mcesa_bits ORed in */
                        kmemleak_not_leak((void *) mcesa_origin);
                        mcesa_bits = MACHINE_HAS_GS ? 11 : 0;
                }
        } else {
                async_stack = pcpu->lowcore->async_stack - ASYNC_FRAME_OFFSET;
                panic_stack = pcpu->lowcore->panic_stack - PANIC_FRAME_OFFSET;
                mcesa_origin = pcpu->lowcore->mcesad & MCESA_ORIGIN_MASK;
                mcesa_bits = pcpu->lowcore->mcesad & MCESA_LC_MASK;
        }
        lc = pcpu->lowcore;
        memcpy(lc, &S390_lowcore, 512);
        memset((char *) lc + 512, 0, sizeof(*lc) - 512);
        lc->async_stack = async_stack + ASYNC_FRAME_OFFSET;
        lc->panic_stack = panic_stack + PANIC_FRAME_OFFSET;
        lc->mcesad = mcesa_origin | mcesa_bits;
        lc->cpu_nr = cpu;
        lc->spinlock_lockval = arch_spin_lockval(cpu);
        lc->br_r1_trampoline = 0x07f1;  /* br %r1 */
        if (vdso_alloc_per_cpu(lc))
                goto out;
        lowcore_ptr[cpu] = lc;
        pcpu_sigp_retry(pcpu, SIGP_SET_PREFIX, (u32)(unsigned long) lc);
        return 0;
out:
        if (pcpu != &pcpu_devices[0]) {
                if (mcesa_origin)
                        kmem_cache_free(pcpu_mcesa_cache,
                                        (void *) mcesa_origin);
                free_page(panic_stack);
                free_pages(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)
{
        unsigned long mcesa_origin;

        pcpu_sigp_retry(pcpu, SIGP_SET_PREFIX, 0);
        lowcore_ptr[pcpu - pcpu_devices] = NULL;
        vdso_free_per_cpu(pcpu->lowcore);
        if (pcpu == &pcpu_devices[0])
                return;
        if (MACHINE_HAS_VX || MACHINE_HAS_GS) {
                mcesa_origin = pcpu->lowcore->mcesad & MCESA_ORIGIN_MASK;
                kmem_cache_free(pcpu_mcesa_cache, (void *) mcesa_origin);
        }
        free_page(pcpu->lowcore->panic_stack-PANIC_FRAME_OFFSET);
        free_pages(pcpu->lowcore->async_stack-ASYNC_FRAME_OFFSET, 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;

        cpumask_set_cpu(cpu, &init_mm.context.cpu_attach_mask);
        cpumask_set_cpu(cpu, mm_cpumask(&init_mm));
        lc->cpu_nr = cpu;
        lc->spinlock_lockval = arch_spin_lockval(cpu);
        lc->percpu_offset = __per_cpu_offset[cpu];
        lc->kernel_asce = S390_lowcore.kernel_asce;
        lc->machine_flags = S390_lowcore.machine_flags;
        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,
               sizeof(lc->stfle_fac_list));
        memcpy(lc->alt_stfle_fac_list, S390_lowcore.alt_stfle_fac_list,
               sizeof(lc->alt_stfle_fac_list));
}

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

        lc->kernel_stack = (unsigned long) task_stack_page(tsk)
                + THREAD_SIZE - STACK_FRAME_OVERHEAD - sizeof(struct pt_regs);
        lc->current_task = (unsigned long) tsk;
        lc->lpp = LPP_MAGIC;
        lc->current_pid = tsk->pid;
        lc->user_timer = tsk->thread.user_timer;
        lc->guest_timer = tsk->thread.guest_timer;
        lc->system_timer = tsk->thread.system_timer;
        lc->hardirq_timer = tsk->thread.hardirq_timer;
        lc->softirq_timer = tsk->thread.softirq_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);
        __bpon();
        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 (;;) ;
}

/*
 * Enable additional logical cpus for multi-threading.
 */
static int pcpu_set_smt(unsigned int mtid)
{
        int cc;

        if (smp_cpu_mtid == mtid)
                return 0;
        cc = __pcpu_sigp(0, SIGP_SET_MULTI_THREADING, mtid, NULL);
        if (cc == 0) {
                smp_cpu_mtid = mtid;
                smp_cpu_mt_shift = 0;
                while (smp_cpu_mtid >= (1U << smp_cpu_mt_shift))
                        smp_cpu_mt_shift++;
                pcpu_devices[0].address = stap();
        }
        return cc;
}

/*
 * 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)
{
        struct lowcore *lc = pcpu_devices->lowcore;

        if (pcpu_devices[0].address == stap())
                lc = &S390_lowcore;

        pcpu_delegate(&pcpu_devices[0], func, data,
                      lc->panic_stack - PANIC_FRAME_OFFSET + 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;
}

bool arch_vcpu_is_preempted(int cpu)
{
        if (test_cpu_flag_of(CIF_ENABLED_WAIT, cpu))
                return false;
        if (pcpu_running(pcpu_devices + cpu))
                return false;
        return true;
}
EXPORT_SYMBOL(arch_vcpu_is_preempted);

void smp_yield_cpu(int cpu)
{
        if (MACHINE_HAS_DIAG9C) {
                diag_stat_inc_norecursion(DIAG_STAT_X09C);
                asm volatile("diag %0,0,0x9c"
                             : : "d" (pcpu_devices[cpu].address));
        } else if (MACHINE_HAS_DIAG44) {
                diag_stat_inc_norecursion(DIAG_STAT_X044);
                asm volatile("diag 0,0,0x44");
        }
}

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

        end = get_tod_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_tod_clock() < end)
                        cpu_relax();
        }
        while (get_tod_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();
        }
}

/*
 * This is the main routine where commands issued by other
 * cpus are handled.
 */
static void smp_handle_ext_call(void)
{
        unsigned long bits;

        /* handle bit signal external calls */
        bits = xchg(&pcpu_devices[smp_processor_id()].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_single, &bits))
                generic_smp_call_function_single_interrupt();
}

static void do_ext_call_interrupt(struct ext_code ext_code,
                                  unsigned int param32, unsigned long param64)
{
        inc_irq_stat(ext_code.code == 0x1202 ? IRQEXT_EXC : IRQEXT_EMS);
        smp_handle_ext_call();
}

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_single);
}

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

/*
 * 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);

#ifdef CONFIG_CRASH_DUMP

int smp_store_status(int cpu)
{
        struct pcpu *pcpu = pcpu_devices + cpu;
        unsigned long pa;

        pa = __pa(&pcpu->lowcore->floating_pt_save_area);
        if (__pcpu_sigp_relax(pcpu->address, SIGP_STORE_STATUS_AT_ADDRESS,
                              pa) != SIGP_CC_ORDER_CODE_ACCEPTED)
                return -EIO;
        if (!MACHINE_HAS_VX && !MACHINE_HAS_GS)
                return 0;
        pa = __pa(pcpu->lowcore->mcesad & MCESA_ORIGIN_MASK);
        if (MACHINE_HAS_GS)
                pa |= pcpu->lowcore->mcesad & MCESA_LC_MASK;
        if (__pcpu_sigp_relax(pcpu->address, SIGP_STORE_ADDITIONAL_STATUS,
                              pa) != SIGP_CC_ORDER_CODE_ACCEPTED)
                return -EIO;
        return 0;
}

/*
 * Collect CPU state of the previous, crashed system.
 * There are four cases:
 * 1) standard zfcp dump
 *    condition: OLDMEM_BASE == NULL && ipl_info.type == IPL_TYPE_FCP_DUMP
 *    The state for all CPUs except the boot CPU needs to be collected
 *    with sigp stop-and-store-status. The boot CPU state is located in
 *    the absolute lowcore of the memory stored in the HSA. The zcore code
 *    will copy the boot CPU state from the HSA.
 * 2) stand-alone kdump for SCSI (zfcp dump with swapped memory)
 *    condition: OLDMEM_BASE != NULL && ipl_info.type == IPL_TYPE_FCP_DUMP
 *    The state for all CPUs except the boot CPU needs to be collected
 *    with sigp stop-and-store-status. The firmware or the boot-loader
 *    stored the registers of the boot CPU in the absolute lowcore in the
 *    memory of the old system.
 * 3) kdump and the old kernel did not store the CPU state,
 *    or stand-alone kdump for DASD
 *    condition: OLDMEM_BASE != NULL && !is_kdump_kernel()
 *    The state for all CPUs except the boot CPU needs to be collected
 *    with sigp stop-and-store-status. The kexec code or the boot-loader
 *    stored the registers of the boot CPU in the memory of the old system.
 * 4) kdump and the old kernel stored the CPU state
 *    condition: OLDMEM_BASE != NULL && is_kdump_kernel()
 *    This case does not exist for s390 anymore, setup_arch explicitly
 *    deactivates the elfcorehdr= kernel parameter
 */
static __init void smp_save_cpu_vxrs(struct save_area *sa, u16 addr,
                                     bool is_boot_cpu, unsigned long page)
{
        __vector128 *vxrs = (__vector128 *) page;

        if (is_boot_cpu)
                vxrs = boot_cpu_vector_save_area;
        else
                __pcpu_sigp_relax(addr, SIGP_STORE_ADDITIONAL_STATUS, page);
        save_area_add_vxrs(sa, vxrs);
}

static __init void smp_save_cpu_regs(struct save_area *sa, u16 addr,
                                     bool is_boot_cpu, unsigned long page)
{
        void *regs = (void *) page;

        if (is_boot_cpu)
                copy_oldmem_kernel(regs, (void *) __LC_FPREGS_SAVE_AREA, 512);
        else
                __pcpu_sigp_relax(addr, SIGP_STORE_STATUS_AT_ADDRESS, page);
        save_area_add_regs(sa, regs);
}

void __init smp_save_dump_cpus(void)
{
        int addr, boot_cpu_addr, max_cpu_addr;
        struct save_area *sa;
        unsigned long page;
        bool is_boot_cpu;

        if (!(OLDMEM_BASE || ipl_info.type == IPL_TYPE_FCP_DUMP))
                /* No previous system present, normal boot. */
                return;
        /* Allocate a page as dumping area for the store status sigps */
        page = memblock_alloc_base(PAGE_SIZE, PAGE_SIZE, 1UL << 31);
        /* Set multi-threading state to the previous system. */
        pcpu_set_smt(sclp.mtid_prev);
        boot_cpu_addr = stap();
        max_cpu_addr = SCLP_MAX_CORES << sclp.mtid_prev;
        for (addr = 0; addr <= max_cpu_addr; addr++) {
                if (__pcpu_sigp_relax(addr, SIGP_SENSE, 0) ==
                    SIGP_CC_NOT_OPERATIONAL)
                        continue;
                is_boot_cpu = (addr == boot_cpu_addr);
                /* Allocate save area */
                sa = save_area_alloc(is_boot_cpu);
                if (!sa)
                        panic("could not allocate memory for save area\n");
                if (MACHINE_HAS_VX)
                        /* Get the vector registers */
                        smp_save_cpu_vxrs(sa, addr, is_boot_cpu, page);
                /*
                 * For a zfcp dump OLDMEM_BASE == NULL and the registers
                 * of the boot CPU are stored in the HSA. To retrieve
                 * these registers an SCLP request is required which is
                 * done by drivers/s390/char/zcore.c:init_cpu_info()
                 */
                if (!is_boot_cpu || OLDMEM_BASE)
                        /* Get the CPU registers */
                        smp_save_cpu_regs(sa, addr, is_boot_cpu, page);
        }
        memblock_free(page, PAGE_SIZE);
        diag308_reset();
        pcpu_set_smt(0);
}
#endif /* 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 void __ref smp_get_core_info(struct sclp_core_info *info, int early)
{
        static int use_sigp_detection;
        int address;

        if (use_sigp_detection || sclp_get_core_info(info, early)) {
                use_sigp_detection = 1;
                for (address = 0;
                     address < (SCLP_MAX_CORES << smp_cpu_mt_shift);
                     address += (1U << smp_cpu_mt_shift)) {
                        if (__pcpu_sigp_relax(address, SIGP_SENSE, 0) ==
                            SIGP_CC_NOT_OPERATIONAL)
                                continue;
                        info->core[info->configured].core_id =
                                address >> smp_cpu_mt_shift;
                        info->configured++;
                }
                info->combined = info->configured;
        }
}

static int smp_add_present_cpu(int cpu);

static int __smp_rescan_cpus(struct sclp_core_info *info, int sysfs_add)
{
        struct pcpu *pcpu;
        cpumask_t avail;
        int cpu, nr, i, j;
        u16 address;

        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 (sclp.has_core_type && info->core[i].type != boot_core_type)
                        continue;
                address = info->core[i].core_id << smp_cpu_mt_shift;
                for (j = 0; j <= smp_cpu_mtid; j++) {
                        if (pcpu_find_address(cpu_present_mask, address + j))
                                continue;
                        pcpu = pcpu_devices + cpu;
                        pcpu->address = address + j;
                        pcpu->state =
                                (cpu >= info->configured*(smp_cpu_mtid + 1)) ?
                                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);
                        if (cpu >= nr_cpu_ids)
                                break;
                }
        }
        return nr;
}

void __init smp_detect_cpus(void)
{
        unsigned int cpu, mtid, c_cpus, s_cpus;
        struct sclp_core_info *info;
        u16 address;

        /* Get CPU information */
        info = memblock_virt_alloc(sizeof(*info), 8);
        smp_get_core_info(info, 1);
        /* Find boot CPU type */
        if (sclp.has_core_type) {
                address = stap();
                for (cpu = 0; cpu < info->combined; cpu++)
                        if (info->core[cpu].core_id == address) {
                                /* The boot cpu dictates the cpu type. */
                                boot_core_type = info->core[cpu].type;
                                break;
                        }
                if (cpu >= info->combined)
                        panic("Could not find boot CPU type");
        }

        /* Set multi-threading state for the current system */
        mtid = boot_core_type ? sclp.mtid : sclp.mtid_cp;
        mtid = (mtid < smp_max_threads) ? mtid : smp_max_threads - 1;
        pcpu_set_smt(mtid);

        /* Print number of CPUs */
        c_cpus = s_cpus = 0;
        for (cpu = 0; cpu < info->combined; cpu++) {
                if (sclp.has_core_type &&
                    info->core[cpu].type != boot_core_type)
                        continue;
                if (cpu < info->configured)
                        c_cpus += smp_cpu_mtid + 1;
                else
                        s_cpus += smp_cpu_mtid + 1;
        }
        pr_info("%d configured CPUs, %d standby CPUs\n", c_cpus, s_cpus);

        /* Add CPUs present at boot */
        get_online_cpus();
        __smp_rescan_cpus(info, 0);
        put_online_cpus();
        memblock_free_early((unsigned long)info, sizeof(*info));
}

/*
 *      Activate a secondary processor.
 */
static void smp_start_secondary(void *cpuvoid)
{
        S390_lowcore.last_update_clock = get_tod_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();
        vtime_init();
        pfault_init();
        notify_cpu_starting(smp_processor_id());
        set_cpu_online(smp_processor_id(), true);
        inc_irq_stat(CPU_RST);
        local_irq_enable();
        cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
}

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

        pcpu = pcpu_devices + cpu;
        if (pcpu->state != CPU_STATE_CONFIGURED)
                return -EIO;
        base = smp_get_base_cpu(cpu);
        for (i = 0; i <= smp_cpu_mtid; i++) {
                if (base + i < nr_cpu_ids)
                        if (cpu_online(base + i))
                                break;
        }
        /*
         * If this is the first CPU of the core to get online
         * do an initial CPU reset.
         */
        if (i > smp_cpu_mtid &&
            pcpu_sigp_retry(pcpu_devices + base, 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);
        /* Wait until cpu puts itself in the online & active maps */
        while (!cpu_online(cpu))
                cpu_relax();
        return 0;
}

static unsigned int setup_possible_cpus __initdata;

static int __init _setup_possible_cpus(char *s)
{
        get_option(&s, &setup_possible_cpus);
        return 0;
}
early_param("possible_cpus", _setup_possible_cpus);

#ifdef CONFIG_HOTPLUG_CPU

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

        /* Handle possible pending IPIs */
        smp_handle_ext_call();
        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);
        clear_cpu_flag(CIF_NOHZ_DELAY);
        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);
        cpumask_clear_cpu(cpu, mm_cpumask(&init_mm));
        cpumask_clear_cpu(cpu, &init_mm.context.cpu_attach_mask);
}

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

#endif /* CONFIG_HOTPLUG_CPU */

void __init smp_fill_possible_mask(void)
{
        unsigned int possible, sclp_max, cpu;

        sclp_max = max(sclp.mtid, sclp.mtid_cp) + 1;
        sclp_max = min(smp_max_threads, sclp_max);
        sclp_max = (sclp.max_cores * sclp_max) ?: nr_cpu_ids;
        possible = setup_possible_cpus ?: nr_cpu_ids;
        possible = min(possible, sclp_max);
        for (cpu = 0; cpu < possible && cpu < nr_cpu_ids; cpu++)
                set_cpu_possible(cpu, true);
}

void __init smp_prepare_cpus(unsigned int max_cpus)
{
        unsigned long size;

        /* request the 0x1201 emergency signal external interrupt */
        if (register_external_irq(EXT_IRQ_EMERGENCY_SIG, do_ext_call_interrupt))
                panic("Couldn't request external interrupt 0x1201");
        /* request the 0x1202 external call external interrupt */
        if (register_external_irq(EXT_IRQ_EXTERNAL_CALL, do_ext_call_interrupt))
                panic("Couldn't request external interrupt 0x1202");
        /* create slab cache for the machine-check-extended-save-areas */
        if (MACHINE_HAS_VX || MACHINE_HAS_GS) {
                size = 1UL << (MACHINE_HAS_GS ? 11 : 10);
                pcpu_mcesa_cache = kmem_cache_create("nmi_save_areas",
                                                     size, size, 0, NULL);
                if (!pcpu_mcesa_cache)
                        panic("Couldn't create nmi save area cache");
        }
}

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

        WARN_ON(!cpu_present(0) || !cpu_online(0));
        pcpu->state = CPU_STATE_CONFIGURED;
        pcpu->lowcore = (struct lowcore *)(unsigned long) store_prefix();
        S390_lowcore.percpu_offset = __per_cpu_offset[0];
        smp_cpu_set_polarization(0, POLARIZATION_UNKNOWN);
}

void __init smp_cpus_done(unsigned int max_cpus)
{
}

void __init smp_setup_processor_id(void)
{
        pcpu_devices[0].address = stap();
        S390_lowcore.cpu_nr = 0;
        S390_lowcore.spinlock_lockval = arch_spin_lockval(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, i;
        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;
        cpu = smp_get_base_cpu(cpu);
        if (cpu == 0)
                goto out;
        for (i = 0; i <= smp_cpu_mtid; i++)
                if (cpu_online(cpu + i))
                        goto out;
        pcpu = pcpu_devices + cpu;
        rc = 0;
        switch (val) {
        case 0:
                if (pcpu->state != CPU_STATE_CONFIGURED)
                        break;
                rc = sclp_core_deconfigure(pcpu->address >> smp_cpu_mt_shift);
                if (rc)
                        break;
                for (i = 0; i <= smp_cpu_mtid; i++) {
                        if (cpu + i >= nr_cpu_ids || !cpu_present(cpu + i))
                                continue;
                        pcpu[i].state = CPU_STATE_STANDBY;
                        smp_cpu_set_polarization(cpu + i,
                                                 POLARIZATION_UNKNOWN);
                }
                topology_expect_change();
                break;
        case 1:
                if (pcpu->state != CPU_STATE_STANDBY)
                        break;
                rc = sclp_core_configure(pcpu->address >> smp_cpu_mt_shift);
                if (rc)
                        break;
                for (i = 0; i <= smp_cpu_mtid; i++) {
                        if (cpu + i >= nr_cpu_ids || !cpu_present(cpu + i))
                                continue;
                        pcpu[i].state = CPU_STATE_CONFIGURED;
                        smp_cpu_set_polarization(cpu + i,
                                                 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 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 smp_cpu_online(unsigned int cpu)
{
        struct device *s = &per_cpu(cpu_device, cpu)->dev;

        return sysfs_create_group(&s->kobj, &cpu_online_attr_group);
}
static int smp_cpu_pre_down(unsigned int cpu)
{
        struct device *s = &per_cpu(cpu_device, cpu)->dev;

        sysfs_remove_group(&s->kobj, &cpu_online_attr_group);
        return 0;
}

static int smp_add_present_cpu(int cpu)
{
        struct device *s;
        struct cpu *c;
        int rc;

        c = kzalloc(sizeof(*c), GFP_KERNEL);
        if (!c)
                return -ENOMEM;
        per_cpu(cpu_device, cpu) = c;
        s = &c->dev;
        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;
        rc = topology_cpu_init(c);
        if (rc)
                goto out_topology;
        return 0;

out_topology:
        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_core_info *info;
        int nr;

        info = kzalloc(sizeof(*info), GFP_KERNEL);
        if (!info)
                return -ENOMEM;
        smp_get_core_info(info, 0);
        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 = lock_device_hotplug_sysfs();
        if (rc)
                return rc;
        rc = smp_rescan_cpus();
        unlock_device_hotplug();
        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 = 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)
                        goto out;
        }

        rc = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "s390/smp:online",
                               smp_cpu_online, smp_cpu_pre_down);
        rc = rc <= 0 ? rc : 0;
out:
        return rc;
}
subsys_initcall(s390_smp_init);