Merge tag 'powerpc-4.13-8' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc...

[mirror_ubuntu-artful-kernel.git] / arch / arm64 / kernel / smp.c

/*
 * SMP initialisation and IPI support
 * Based on arch/arm/kernel/smp.c
 *
 * Copyright (C) 2012 ARM Ltd.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <linux/acpi.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/sched/mm.h>
#include <linux/sched/hotplug.h>
#include <linux/sched/task_stack.h>
#include <linux/interrupt.h>
#include <linux/cache.h>
#include <linux/profile.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/err.h>
#include <linux/cpu.h>
#include <linux/smp.h>
#include <linux/seq_file.h>
#include <linux/irq.h>
#include <linux/percpu.h>
#include <linux/clockchips.h>
#include <linux/completion.h>
#include <linux/of.h>
#include <linux/irq_work.h>
#include <linux/kexec.h>

#include <asm/alternative.h>
#include <asm/atomic.h>
#include <asm/cacheflush.h>
#include <asm/cpu.h>
#include <asm/cputype.h>
#include <asm/cpu_ops.h>
#include <asm/mmu_context.h>
#include <asm/numa.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
#include <asm/processor.h>
#include <asm/smp_plat.h>
#include <asm/sections.h>
#include <asm/tlbflush.h>
#include <asm/ptrace.h>
#include <asm/virt.h>

#define CREATE_TRACE_POINTS
#include <trace/events/ipi.h>

DEFINE_PER_CPU_READ_MOSTLY(int, cpu_number);
EXPORT_PER_CPU_SYMBOL(cpu_number);

/*
 * as from 2.5, kernels no longer have an init_tasks structure
 * so we need some other way of telling a new secondary core
 * where to place its SVC stack
 */
struct secondary_data secondary_data;
/* Number of CPUs which aren't online, but looping in kernel text. */
int cpus_stuck_in_kernel;

enum ipi_msg_type {
        IPI_RESCHEDULE,
        IPI_CALL_FUNC,
        IPI_CPU_STOP,
        IPI_CPU_CRASH_STOP,
        IPI_TIMER,
        IPI_IRQ_WORK,
        IPI_WAKEUP
};

#ifdef CONFIG_ARM64_VHE

/* Whether the boot CPU is running in HYP mode or not*/
static bool boot_cpu_hyp_mode;

static inline void save_boot_cpu_run_el(void)
{
        boot_cpu_hyp_mode = is_kernel_in_hyp_mode();
}

static inline bool is_boot_cpu_in_hyp_mode(void)
{
        return boot_cpu_hyp_mode;
}

/*
 * Verify that a secondary CPU is running the kernel at the same
 * EL as that of the boot CPU.
 */
void verify_cpu_run_el(void)
{
        bool in_el2 = is_kernel_in_hyp_mode();
        bool boot_cpu_el2 = is_boot_cpu_in_hyp_mode();

        if (in_el2 ^ boot_cpu_el2) {
                pr_crit("CPU%d: mismatched Exception Level(EL%d) with boot CPU(EL%d)\n",
                                        smp_processor_id(),
                                        in_el2 ? 2 : 1,
                                        boot_cpu_el2 ? 2 : 1);
                cpu_panic_kernel();
        }
}

#else
static inline void save_boot_cpu_run_el(void) {}
#endif

#ifdef CONFIG_HOTPLUG_CPU
static int op_cpu_kill(unsigned int cpu);
#else
static inline int op_cpu_kill(unsigned int cpu)
{
        return -ENOSYS;
}
#endif


/*
 * Boot a secondary CPU, and assign it the specified idle task.
 * This also gives us the initial stack to use for this CPU.
 */
static int boot_secondary(unsigned int cpu, struct task_struct *idle)
{
        if (cpu_ops[cpu]->cpu_boot)
                return cpu_ops[cpu]->cpu_boot(cpu);

        return -EOPNOTSUPP;
}

static DECLARE_COMPLETION(cpu_running);

int __cpu_up(unsigned int cpu, struct task_struct *idle)
{
        int ret;
        long status;

        /*
         * We need to tell the secondary core where to find its stack and the
         * page tables.
         */
        secondary_data.task = idle;
        secondary_data.stack = task_stack_page(idle) + THREAD_START_SP;
        update_cpu_boot_status(CPU_MMU_OFF);
        __flush_dcache_area(&secondary_data, sizeof(secondary_data));

        /*
         * Now bring the CPU into our world.
         */
        ret = boot_secondary(cpu, idle);
        if (ret == 0) {
                /*
                 * CPU was successfully started, wait for it to come online or
                 * time out.
                 */
                wait_for_completion_timeout(&cpu_running,
                                            msecs_to_jiffies(1000));

                if (!cpu_online(cpu)) {
                        pr_crit("CPU%u: failed to come online\n", cpu);
                        ret = -EIO;
                }
        } else {
                pr_err("CPU%u: failed to boot: %d\n", cpu, ret);
        }

        secondary_data.task = NULL;
        secondary_data.stack = NULL;
        status = READ_ONCE(secondary_data.status);
        if (ret && status) {

                if (status == CPU_MMU_OFF)
                        status = READ_ONCE(__early_cpu_boot_status);

                switch (status) {
                default:
                        pr_err("CPU%u: failed in unknown state : 0x%lx\n",
                                        cpu, status);
                        break;
                case CPU_KILL_ME:
                        if (!op_cpu_kill(cpu)) {
                                pr_crit("CPU%u: died during early boot\n", cpu);
                                break;
                        }
                        /* Fall through */
                        pr_crit("CPU%u: may not have shut down cleanly\n", cpu);
                case CPU_STUCK_IN_KERNEL:
                        pr_crit("CPU%u: is stuck in kernel\n", cpu);
                        cpus_stuck_in_kernel++;
                        break;
                case CPU_PANIC_KERNEL:
                        panic("CPU%u detected unsupported configuration\n", cpu);
                }
        }

        return ret;
}

/*
 * This is the secondary CPU boot entry.  We're using this CPUs
 * idle thread stack, but a set of temporary page tables.
 */
asmlinkage void secondary_start_kernel(void)
{
        struct mm_struct *mm = &init_mm;
        unsigned int cpu;

        cpu = task_cpu(current);
        set_my_cpu_offset(per_cpu_offset(cpu));

        /*
         * All kernel threads share the same mm context; grab a
         * reference and switch to it.
         */
        mmgrab(mm);
        current->active_mm = mm;

        /*
         * TTBR0 is only used for the identity mapping at this stage. Make it
         * point to zero page to avoid speculatively fetching new entries.
         */
        cpu_uninstall_idmap();

        preempt_disable();
        trace_hardirqs_off();

        /*
         * If the system has established the capabilities, make sure
         * this CPU ticks all of those. If it doesn't, the CPU will
         * fail to come online.
         */
        check_local_cpu_capabilities();

        if (cpu_ops[cpu]->cpu_postboot)
                cpu_ops[cpu]->cpu_postboot();

        /*
         * Log the CPU info before it is marked online and might get read.
         */
        cpuinfo_store_cpu();

        /*
         * Enable GIC and timers.
         */
        notify_cpu_starting(cpu);

        store_cpu_topology(cpu);

        /*
         * OK, now it's safe to let the boot CPU continue.  Wait for
         * the CPU migration code to notice that the CPU is online
         * before we continue.
         */
        pr_info("CPU%u: Booted secondary processor [%08x]\n",
                                         cpu, read_cpuid_id());
        update_cpu_boot_status(CPU_BOOT_SUCCESS);
        set_cpu_online(cpu, true);
        complete(&cpu_running);

        local_irq_enable();
        local_async_enable();

        /*
         * OK, it's off to the idle thread for us
         */
        cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
}

#ifdef CONFIG_HOTPLUG_CPU
static int op_cpu_disable(unsigned int cpu)
{
        /*
         * If we don't have a cpu_die method, abort before we reach the point
         * of no return. CPU0 may not have an cpu_ops, so test for it.
         */
        if (!cpu_ops[cpu] || !cpu_ops[cpu]->cpu_die)
                return -EOPNOTSUPP;

        /*
         * We may need to abort a hot unplug for some other mechanism-specific
         * reason.
         */
        if (cpu_ops[cpu]->cpu_disable)
                return cpu_ops[cpu]->cpu_disable(cpu);

        return 0;
}

/*
 * __cpu_disable runs on the processor to be shutdown.
 */
int __cpu_disable(void)
{
        unsigned int cpu = smp_processor_id();
        int ret;

        ret = op_cpu_disable(cpu);
        if (ret)
                return ret;

        /*
         * Take this CPU offline.  Once we clear this, we can't return,
         * and we must not schedule until we're ready to give up the cpu.
         */
        set_cpu_online(cpu, false);

        /*
         * OK - migrate IRQs away from this CPU
         */
        irq_migrate_all_off_this_cpu();

        return 0;
}

static int op_cpu_kill(unsigned int cpu)
{
        /*
         * If we have no means of synchronising with the dying CPU, then assume
         * that it is really dead. We can only wait for an arbitrary length of
         * time and hope that it's dead, so let's skip the wait and just hope.
         */
        if (!cpu_ops[cpu]->cpu_kill)
                return 0;

        return cpu_ops[cpu]->cpu_kill(cpu);
}

/*
 * called on the thread which is asking for a CPU to be shutdown -
 * waits until shutdown has completed, or it is timed out.
 */
void __cpu_die(unsigned int cpu)
{
        int err;

        if (!cpu_wait_death(cpu, 5)) {
                pr_crit("CPU%u: cpu didn't die\n", cpu);
                return;
        }
        pr_notice("CPU%u: shutdown\n", cpu);

        /*
         * Now that the dying CPU is beyond the point of no return w.r.t.
         * in-kernel synchronisation, try to get the firwmare to help us to
         * verify that it has really left the kernel before we consider
         * clobbering anything it might still be using.
         */
        err = op_cpu_kill(cpu);
        if (err)
                pr_warn("CPU%d may not have shut down cleanly: %d\n",
                        cpu, err);
}

/*
 * Called from the idle thread for the CPU which has been shutdown.
 *
 * Note that we disable IRQs here, but do not re-enable them
 * before returning to the caller. This is also the behaviour
 * of the other hotplug-cpu capable cores, so presumably coming
 * out of idle fixes this.
 */
void cpu_die(void)
{
        unsigned int cpu = smp_processor_id();

        idle_task_exit();

        local_irq_disable();

        /* Tell __cpu_die() that this CPU is now safe to dispose of */
        (void)cpu_report_death();

        /*
         * Actually shutdown the CPU. This must never fail. The specific hotplug
         * mechanism must perform all required cache maintenance to ensure that
         * no dirty lines are lost in the process of shutting down the CPU.
         */
        cpu_ops[cpu]->cpu_die(cpu);

        BUG();
}
#endif

/*
 * Kill the calling secondary CPU, early in bringup before it is turned
 * online.
 */
void cpu_die_early(void)
{
        int cpu = smp_processor_id();

        pr_crit("CPU%d: will not boot\n", cpu);

        /* Mark this CPU absent */
        set_cpu_present(cpu, 0);

#ifdef CONFIG_HOTPLUG_CPU
        update_cpu_boot_status(CPU_KILL_ME);
        /* Check if we can park ourselves */
        if (cpu_ops[cpu] && cpu_ops[cpu]->cpu_die)
                cpu_ops[cpu]->cpu_die(cpu);
#endif
        update_cpu_boot_status(CPU_STUCK_IN_KERNEL);

        cpu_park_loop();
}

static void __init hyp_mode_check(void)
{
        if (is_hyp_mode_available())
                pr_info("CPU: All CPU(s) started at EL2\n");
        else if (is_hyp_mode_mismatched())
                WARN_TAINT(1, TAINT_CPU_OUT_OF_SPEC,
                           "CPU: CPUs started in inconsistent modes");
        else
                pr_info("CPU: All CPU(s) started at EL1\n");
}

void __init smp_cpus_done(unsigned int max_cpus)
{
        pr_info("SMP: Total of %d processors activated.\n", num_online_cpus());
        setup_cpu_features();
        hyp_mode_check();
        apply_alternatives_all();
        mark_linear_text_alias_ro();
}

void __init smp_prepare_boot_cpu(void)
{
        set_my_cpu_offset(per_cpu_offset(smp_processor_id()));
        /*
         * Initialise the static keys early as they may be enabled by the
         * cpufeature code.
         */
        jump_label_init();
        cpuinfo_store_boot_cpu();
        save_boot_cpu_run_el();
        /*
         * Run the errata work around checks on the boot CPU, once we have
         * initialised the cpu feature infrastructure from
         * cpuinfo_store_boot_cpu() above.
         */
        update_cpu_errata_workarounds();
}

static u64 __init of_get_cpu_mpidr(struct device_node *dn)
{
        const __be32 *cell;
        u64 hwid;

        /*
         * A cpu node with missing "reg" property is
         * considered invalid to build a cpu_logical_map
         * entry.
         */
        cell = of_get_property(dn, "reg", NULL);
        if (!cell) {
                pr_err("%pOF: missing reg property\n", dn);
                return INVALID_HWID;
        }

        hwid = of_read_number(cell, of_n_addr_cells(dn));
        /*
         * Non affinity bits must be set to 0 in the DT
         */
        if (hwid & ~MPIDR_HWID_BITMASK) {
                pr_err("%pOF: invalid reg property\n", dn);
                return INVALID_HWID;
        }
        return hwid;
}

/*
 * Duplicate MPIDRs are a recipe for disaster. Scan all initialized
 * entries and check for duplicates. If any is found just ignore the
 * cpu. cpu_logical_map was initialized to INVALID_HWID to avoid
 * matching valid MPIDR values.
 */
static bool __init is_mpidr_duplicate(unsigned int cpu, u64 hwid)
{
        unsigned int i;

        for (i = 1; (i < cpu) && (i < NR_CPUS); i++)
                if (cpu_logical_map(i) == hwid)
                        return true;
        return false;
}

/*
 * Initialize cpu operations for a logical cpu and
 * set it in the possible mask on success
 */
static int __init smp_cpu_setup(int cpu)
{
        if (cpu_read_ops(cpu))
                return -ENODEV;

        if (cpu_ops[cpu]->cpu_init(cpu))
                return -ENODEV;

        set_cpu_possible(cpu, true);

        return 0;
}

static bool bootcpu_valid __initdata;
static unsigned int cpu_count = 1;

#ifdef CONFIG_ACPI
static struct acpi_madt_generic_interrupt cpu_madt_gicc[NR_CPUS];

struct acpi_madt_generic_interrupt *acpi_cpu_get_madt_gicc(int cpu)
{
        return &cpu_madt_gicc[cpu];
}

/*
 * acpi_map_gic_cpu_interface - parse processor MADT entry
 *
 * Carry out sanity checks on MADT processor entry and initialize
 * cpu_logical_map on success
 */
static void __init
acpi_map_gic_cpu_interface(struct acpi_madt_generic_interrupt *processor)
{
        u64 hwid = processor->arm_mpidr;

        if (!(processor->flags & ACPI_MADT_ENABLED)) {
                pr_debug("skipping disabled CPU entry with 0x%llx MPIDR\n", hwid);
                return;
        }

        if (hwid & ~MPIDR_HWID_BITMASK || hwid == INVALID_HWID) {
                pr_err("skipping CPU entry with invalid MPIDR 0x%llx\n", hwid);
                return;
        }

        if (is_mpidr_duplicate(cpu_count, hwid)) {
                pr_err("duplicate CPU MPIDR 0x%llx in MADT\n", hwid);
                return;
        }

        /* Check if GICC structure of boot CPU is available in the MADT */
        if (cpu_logical_map(0) == hwid) {
                if (bootcpu_valid) {
                        pr_err("duplicate boot CPU MPIDR: 0x%llx in MADT\n",
                               hwid);
                        return;
                }
                bootcpu_valid = true;
                cpu_madt_gicc[0] = *processor;
                early_map_cpu_to_node(0, acpi_numa_get_nid(0, hwid));
                return;
        }

        if (cpu_count >= NR_CPUS)
                return;

        /* map the logical cpu id to cpu MPIDR */
        cpu_logical_map(cpu_count) = hwid;

        cpu_madt_gicc[cpu_count] = *processor;

        /*
         * Set-up the ACPI parking protocol cpu entries
         * while initializing the cpu_logical_map to
         * avoid parsing MADT entries multiple times for
         * nothing (ie a valid cpu_logical_map entry should
         * contain a valid parking protocol data set to
         * initialize the cpu if the parking protocol is
         * the only available enable method).
         */
        acpi_set_mailbox_entry(cpu_count, processor);

        early_map_cpu_to_node(cpu_count, acpi_numa_get_nid(cpu_count, hwid));

        cpu_count++;
}

static int __init
acpi_parse_gic_cpu_interface(struct acpi_subtable_header *header,
                             const unsigned long end)
{
        struct acpi_madt_generic_interrupt *processor;

        processor = (struct acpi_madt_generic_interrupt *)header;
        if (BAD_MADT_GICC_ENTRY(processor, end))
                return -EINVAL;

        acpi_table_print_madt_entry(header);

        acpi_map_gic_cpu_interface(processor);

        return 0;
}
#else
#define acpi_table_parse_madt(...)      do { } while (0)
#endif

/*
 * Enumerate the possible CPU set from the device tree and build the
 * cpu logical map array containing MPIDR values related to logical
 * cpus. Assumes that cpu_logical_map(0) has already been initialized.
 */
static void __init of_parse_and_init_cpus(void)
{
        struct device_node *dn;

        for_each_node_by_type(dn, "cpu") {
                u64 hwid = of_get_cpu_mpidr(dn);

                if (hwid == INVALID_HWID)
                        goto next;

                if (is_mpidr_duplicate(cpu_count, hwid)) {
                        pr_err("%pOF: duplicate cpu reg properties in the DT\n",
                                dn);
                        goto next;
                }

                /*
                 * The numbering scheme requires that the boot CPU
                 * must be assigned logical id 0. Record it so that
                 * the logical map built from DT is validated and can
                 * be used.
                 */
                if (hwid == cpu_logical_map(0)) {
                        if (bootcpu_valid) {
                                pr_err("%pOF: duplicate boot cpu reg property in DT\n",
                                        dn);
                                goto next;
                        }

                        bootcpu_valid = true;
                        early_map_cpu_to_node(0, of_node_to_nid(dn));

                        /*
                         * cpu_logical_map has already been
                         * initialized and the boot cpu doesn't need
                         * the enable-method so continue without
                         * incrementing cpu.
                         */
                        continue;
                }

                if (cpu_count >= NR_CPUS)
                        goto next;

                pr_debug("cpu logical map 0x%llx\n", hwid);
                cpu_logical_map(cpu_count) = hwid;

                early_map_cpu_to_node(cpu_count, of_node_to_nid(dn));
next:
                cpu_count++;
        }
}

/*
 * Enumerate the possible CPU set from the device tree or ACPI and build the
 * cpu logical map array containing MPIDR values related to logical
 * cpus. Assumes that cpu_logical_map(0) has already been initialized.
 */
void __init smp_init_cpus(void)
{
        int i;

        if (acpi_disabled)
                of_parse_and_init_cpus();
        else
                /*
                 * do a walk of MADT to determine how many CPUs
                 * we have including disabled CPUs, and get information
                 * we need for SMP init
                 */
                acpi_table_parse_madt(ACPI_MADT_TYPE_GENERIC_INTERRUPT,
                                      acpi_parse_gic_cpu_interface, 0);

        if (cpu_count > nr_cpu_ids)
                pr_warn("Number of cores (%d) exceeds configured maximum of %d - clipping\n",
                        cpu_count, nr_cpu_ids);

        if (!bootcpu_valid) {
                pr_err("missing boot CPU MPIDR, not enabling secondaries\n");
                return;
        }

        /*
         * We need to set the cpu_logical_map entries before enabling
         * the cpus so that cpu processor description entries (DT cpu nodes
         * and ACPI MADT entries) can be retrieved by matching the cpu hwid
         * with entries in cpu_logical_map while initializing the cpus.
         * If the cpu set-up fails, invalidate the cpu_logical_map entry.
         */
        for (i = 1; i < nr_cpu_ids; i++) {
                if (cpu_logical_map(i) != INVALID_HWID) {
                        if (smp_cpu_setup(i))
                                cpu_logical_map(i) = INVALID_HWID;
                }
        }
}

void __init smp_prepare_cpus(unsigned int max_cpus)
{
        int err;
        unsigned int cpu;
        unsigned int this_cpu;

        init_cpu_topology();

        this_cpu = smp_processor_id();
        store_cpu_topology(this_cpu);
        numa_store_cpu_info(this_cpu);

        /*
         * If UP is mandated by "nosmp" (which implies "maxcpus=0"), don't set
         * secondary CPUs present.
         */
        if (max_cpus == 0)
                return;

        /*
         * Initialise the present map (which describes the set of CPUs
         * actually populated at the present time) and release the
         * secondaries from the bootloader.
         */
        for_each_possible_cpu(cpu) {

                per_cpu(cpu_number, cpu) = cpu;

                if (cpu == smp_processor_id())
                        continue;

                if (!cpu_ops[cpu])
                        continue;

                err = cpu_ops[cpu]->cpu_prepare(cpu);
                if (err)
                        continue;

                set_cpu_present(cpu, true);
                numa_store_cpu_info(cpu);
        }
}

void (*__smp_cross_call)(const struct cpumask *, unsigned int);

void __init set_smp_cross_call(void (*fn)(const struct cpumask *, unsigned int))
{
        __smp_cross_call = fn;
}

static const char *ipi_types[NR_IPI] __tracepoint_string = {
#define S(x,s)  [x] = s
        S(IPI_RESCHEDULE, "Rescheduling interrupts"),
        S(IPI_CALL_FUNC, "Function call interrupts"),
        S(IPI_CPU_STOP, "CPU stop interrupts"),
        S(IPI_CPU_CRASH_STOP, "CPU stop (for crash dump) interrupts"),
        S(IPI_TIMER, "Timer broadcast interrupts"),
        S(IPI_IRQ_WORK, "IRQ work interrupts"),
        S(IPI_WAKEUP, "CPU wake-up interrupts"),
};

static void smp_cross_call(const struct cpumask *target, unsigned int ipinr)
{
        trace_ipi_raise(target, ipi_types[ipinr]);
        __smp_cross_call(target, ipinr);
}

void show_ipi_list(struct seq_file *p, int prec)
{
        unsigned int cpu, i;

        for (i = 0; i < NR_IPI; i++) {
                seq_printf(p, "%*s%u:%s", prec - 1, "IPI", i,
                           prec >= 4 ? " " : "");
                for_each_online_cpu(cpu)
                        seq_printf(p, "%10u ",
                                   __get_irq_stat(cpu, ipi_irqs[i]));
                seq_printf(p, "      %s\n", ipi_types[i]);
        }
}

u64 smp_irq_stat_cpu(unsigned int cpu)
{
        u64 sum = 0;
        int i;

        for (i = 0; i < NR_IPI; i++)
                sum += __get_irq_stat(cpu, ipi_irqs[i]);

        return sum;
}

void arch_send_call_function_ipi_mask(const struct cpumask *mask)
{
        smp_cross_call(mask, IPI_CALL_FUNC);
}

void arch_send_call_function_single_ipi(int cpu)
{
        smp_cross_call(cpumask_of(cpu), IPI_CALL_FUNC);
}

#ifdef CONFIG_ARM64_ACPI_PARKING_PROTOCOL
void arch_send_wakeup_ipi_mask(const struct cpumask *mask)
{
        smp_cross_call(mask, IPI_WAKEUP);
}
#endif

#ifdef CONFIG_IRQ_WORK
void arch_irq_work_raise(void)
{
        if (__smp_cross_call)
                smp_cross_call(cpumask_of(smp_processor_id()), IPI_IRQ_WORK);
}
#endif

/*
 * ipi_cpu_stop - handle IPI from smp_send_stop()
 */
static void ipi_cpu_stop(unsigned int cpu)
{
        set_cpu_online(cpu, false);

        local_irq_disable();

        while (1)
                cpu_relax();
}

#ifdef CONFIG_KEXEC_CORE
static atomic_t waiting_for_crash_ipi = ATOMIC_INIT(0);
#endif

static void ipi_cpu_crash_stop(unsigned int cpu, struct pt_regs *regs)
{
#ifdef CONFIG_KEXEC_CORE
        crash_save_cpu(regs, cpu);

        atomic_dec(&waiting_for_crash_ipi);

        local_irq_disable();

#ifdef CONFIG_HOTPLUG_CPU
        if (cpu_ops[cpu]->cpu_die)
                cpu_ops[cpu]->cpu_die(cpu);
#endif

        /* just in case */
        cpu_park_loop();
#endif
}

/*
 * Main handler for inter-processor interrupts
 */
void handle_IPI(int ipinr, struct pt_regs *regs)
{
        unsigned int cpu = smp_processor_id();
        struct pt_regs *old_regs = set_irq_regs(regs);

        if ((unsigned)ipinr < NR_IPI) {
                trace_ipi_entry_rcuidle(ipi_types[ipinr]);
                __inc_irq_stat(cpu, ipi_irqs[ipinr]);
        }

        switch (ipinr) {
        case IPI_RESCHEDULE:
                scheduler_ipi();
                break;

        case IPI_CALL_FUNC:
                irq_enter();
                generic_smp_call_function_interrupt();
                irq_exit();
                break;

        case IPI_CPU_STOP:
                irq_enter();
                ipi_cpu_stop(cpu);
                irq_exit();
                break;

        case IPI_CPU_CRASH_STOP:
                if (IS_ENABLED(CONFIG_KEXEC_CORE)) {
                        irq_enter();
                        ipi_cpu_crash_stop(cpu, regs);

                        unreachable();
                }
                break;

#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
        case IPI_TIMER:
                irq_enter();
                tick_receive_broadcast();
                irq_exit();
                break;
#endif

#ifdef CONFIG_IRQ_WORK
        case IPI_IRQ_WORK:
                irq_enter();
                irq_work_run();
                irq_exit();
                break;
#endif

#ifdef CONFIG_ARM64_ACPI_PARKING_PROTOCOL
        case IPI_WAKEUP:
                WARN_ONCE(!acpi_parking_protocol_valid(cpu),
                          "CPU%u: Wake-up IPI outside the ACPI parking protocol\n",
                          cpu);
                break;
#endif

        default:
                pr_crit("CPU%u: Unknown IPI message 0x%x\n", cpu, ipinr);
                break;
        }

        if ((unsigned)ipinr < NR_IPI)
                trace_ipi_exit_rcuidle(ipi_types[ipinr]);
        set_irq_regs(old_regs);
}

void smp_send_reschedule(int cpu)
{
        smp_cross_call(cpumask_of(cpu), IPI_RESCHEDULE);
}

#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
void tick_broadcast(const struct cpumask *mask)
{
        smp_cross_call(mask, IPI_TIMER);
}
#endif

void smp_send_stop(void)
{
        unsigned long timeout;

        if (num_online_cpus() > 1) {
                cpumask_t mask;

                cpumask_copy(&mask, cpu_online_mask);
                cpumask_clear_cpu(smp_processor_id(), &mask);

                if (system_state <= SYSTEM_RUNNING)
                        pr_crit("SMP: stopping secondary CPUs\n");
                smp_cross_call(&mask, IPI_CPU_STOP);
        }

        /* Wait up to one second for other CPUs to stop */
        timeout = USEC_PER_SEC;
        while (num_online_cpus() > 1 && timeout--)
                udelay(1);

        if (num_online_cpus() > 1)
                pr_warning("SMP: failed to stop secondary CPUs %*pbl\n",
                           cpumask_pr_args(cpu_online_mask));
}

#ifdef CONFIG_KEXEC_CORE
void smp_send_crash_stop(void)
{
        cpumask_t mask;
        unsigned long timeout;

        if (num_online_cpus() == 1)
                return;

        cpumask_copy(&mask, cpu_online_mask);
        cpumask_clear_cpu(smp_processor_id(), &mask);

        atomic_set(&waiting_for_crash_ipi, num_online_cpus() - 1);

        pr_crit("SMP: stopping secondary CPUs\n");
        smp_cross_call(&mask, IPI_CPU_CRASH_STOP);

        /* Wait up to one second for other CPUs to stop */
        timeout = USEC_PER_SEC;
        while ((atomic_read(&waiting_for_crash_ipi) > 0) && timeout--)
                udelay(1);

        if (atomic_read(&waiting_for_crash_ipi) > 0)
                pr_warning("SMP: failed to stop secondary CPUs %*pbl\n",
                           cpumask_pr_args(&mask));
}

bool smp_crash_stop_failed(void)
{
        return (atomic_read(&waiting_for_crash_ipi) > 0);
}
#endif

/*
 * not supported here
 */
int setup_profiling_timer(unsigned int multiplier)
{
        return -EINVAL;
}

static bool have_cpu_die(void)
{
#ifdef CONFIG_HOTPLUG_CPU
        int any_cpu = raw_smp_processor_id();

        if (cpu_ops[any_cpu] && cpu_ops[any_cpu]->cpu_die)
                return true;
#endif
        return false;
}

bool cpus_are_stuck_in_kernel(void)
{
        bool smp_spin_tables = (num_possible_cpus() > 1 && !have_cpu_die());

        return !!cpus_stuck_in_kernel || smp_spin_tables;
}