// SPDX-License-Identifier: GPL-2.0-only
/*
 * SMP initialisation and IPI support
 * Based on arch/arm/kernel/smp.c
 *
 * Copyright (C) 2012 ARM Ltd.
 */

#include <linux/acpi.h>
#include <linux/arm_sdei.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/irqchip/arm-gic-v3.h>
#include <linux/percpu.h>
#include <linux/clockchips.h>
#include <linux/completion.h>
#include <linux/of.h>
#include <linux/irq_work.h>
#include <linux/kernel_stat.h>
#include <linux/kexec.h>
#include <linux/kgdb.h>
#include <linux/kvm_host.h>
#include <linux/nmi.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/daifflags.h>
#include <asm/kvm_mmu.h>
#include <asm/mmu_context.h>
#include <asm/numa.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>

#include <trace/events/ipi.h>

/*
 * 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. */
static int cpus_stuck_in_kernel;

static int ipi_irq_base __ro_after_init;
static int nr_ipi __ro_after_init = NR_IPI;

struct ipi_descs {
        struct irq_desc *descs[MAX_IPI];
};

static DEFINE_PER_CPU_READ_MOSTLY(struct ipi_descs, pcpu_ipi_desc);

#define get_ipi_desc(__cpu, __ipi) (per_cpu_ptr(&pcpu_ipi_desc, __cpu)->descs[__ipi])

static bool percpu_ipi_descs __ro_after_init;

static bool crash_stop;

static void ipi_setup(int cpu);

#ifdef CONFIG_HOTPLUG_CPU
static void ipi_teardown(int 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)
{
        const struct cpu_operations *ops = get_cpu_ops(cpu);

        if (ops->cpu_boot)
                return ops->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;
        update_cpu_boot_status(CPU_MMU_OFF);

        /* Now bring the CPU into our world */
        ret = boot_secondary(cpu, idle);
        if (ret) {
                if (ret != -EPERM)
                        pr_err("CPU%u: failed to boot: %d\n", cpu, ret);
                return ret;
        }

        /*
         * CPU was successfully started, wait for it to come online or
         * time out.
         */
        wait_for_completion_timeout(&cpu_running,
                                    msecs_to_jiffies(5000));
        if (cpu_online(cpu))
                return 0;

        pr_crit("CPU%u: failed to come online\n", cpu);
        secondary_data.task = NULL;
        status = READ_ONCE(secondary_data.status);
        if (status == CPU_MMU_OFF)
                status = READ_ONCE(__early_cpu_boot_status);

        switch (status & CPU_BOOT_STATUS_MASK) {
        default:
                pr_err("CPU%u: failed in unknown state : 0x%lx\n",
                       cpu, status);
                cpus_stuck_in_kernel++;
                break;
        case CPU_KILL_ME:
                if (!op_cpu_kill(cpu)) {
                        pr_crit("CPU%u: died during early boot\n", cpu);
                        break;
                }
                pr_crit("CPU%u: may not have shut down cleanly\n", cpu);
                fallthrough;
        case CPU_STUCK_IN_KERNEL:
                pr_crit("CPU%u: is stuck in kernel\n", cpu);
                if (status & CPU_STUCK_REASON_52_BIT_VA)
                        pr_crit("CPU%u: does not support 52-bit VAs\n", cpu);
                if (status & CPU_STUCK_REASON_NO_GRAN) {
                        pr_crit("CPU%u: does not support %luK granule\n",
                                cpu, PAGE_SIZE / SZ_1K);
                }
                cpus_stuck_in_kernel++;
                break;
        case CPU_PANIC_KERNEL:
                panic("CPU%u detected unsupported configuration\n", cpu);
        }

        return -EIO;
}

static void init_gic_priority_masking(void)
{
        u32 cpuflags;

        if (WARN_ON(!gic_enable_sre()))
                return;

        cpuflags = read_sysreg(daif);

        WARN_ON(!(cpuflags & PSR_I_BIT));
        WARN_ON(!(cpuflags & PSR_F_BIT));

        gic_write_pmr(GIC_PRIO_IRQON | GIC_PRIO_PSR_I_SET);
}

/*
 * This is the secondary CPU boot entry.  We're using this CPUs
 * idle thread stack, but a set of temporary page tables.
 */
asmlinkage notrace void secondary_start_kernel(void)
{
        u64 mpidr = read_cpuid_mpidr() & MPIDR_HWID_BITMASK;
        struct mm_struct *mm = &init_mm;
        const struct cpu_operations *ops;
        unsigned int cpu = smp_processor_id();

        /*
         * 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();

        if (system_uses_irq_prio_masking())
                init_gic_priority_masking();

        rcutree_report_cpu_starting(cpu);
        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();

        ops = get_cpu_ops(cpu);
        if (ops->cpu_postboot)
                ops->cpu_postboot();

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

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

        ipi_setup(cpu);

        numa_add_cpu(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 0x%010lx [0x%08x]\n",
                                         cpu, (unsigned long)mpidr,
                                         read_cpuid_id());
        update_cpu_boot_status(CPU_BOOT_SUCCESS);
        set_cpu_online(cpu, true);
        complete(&cpu_running);

        /*
         * Secondary CPUs enter the kernel with all DAIF exceptions masked.
         *
         * As with setup_arch() we must unmask Debug and SError exceptions, and
         * as the root irqchip has already been detected and initialized we can
         * unmask IRQ and FIQ at the same time.
         */
        local_daif_restore(DAIF_PROCCTX);

        /*
         * 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)
{
        const struct cpu_operations *ops = get_cpu_ops(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 (!ops || !ops->cpu_die)
                return -EOPNOTSUPP;

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

        remove_cpu_topology(cpu);
        numa_remove_cpu(cpu);

        /*
         * 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);
        ipi_teardown(cpu);

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

        return 0;
}

static int op_cpu_kill(unsigned int cpu)
{
        const struct cpu_operations *ops = get_cpu_ops(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 (!ops->cpu_kill)
                return 0;

        return ops->cpu_kill(cpu);
}

/*
 * Called on the thread which is asking for a CPU to be shutdown after the
 * shutdown completed.
 */
void arch_cpuhp_cleanup_dead_cpu(unsigned int cpu)
{
        int err;

        pr_debug("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 firmware 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.
 *
 */
void __noreturn cpu_die(void)
{
        unsigned int cpu = smp_processor_id();
        const struct cpu_operations *ops = get_cpu_ops(cpu);

        idle_task_exit();

        local_daif_mask();

        /* Tell cpuhp_bp_sync_dead() that this CPU is now safe to dispose of */
        cpuhp_ap_report_dead();

        /*
         * 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.
         */
        ops->cpu_die(cpu);

        BUG();
}
#endif

static void __cpu_try_die(int cpu)
{
#ifdef CONFIG_HOTPLUG_CPU
        const struct cpu_operations *ops = get_cpu_ops(cpu);

        if (ops && ops->cpu_die)
                ops->cpu_die(cpu);
#endif
}

/*
 * Kill the calling secondary CPU, early in bringup before it is turned
 * online.
 */
void __noreturn 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);
        rcutree_report_cpu_dead();

        if (IS_ENABLED(CONFIG_HOTPLUG_CPU)) {
                update_cpu_boot_status(CPU_KILL_ME);
                __cpu_try_die(cpu);
        }

        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");
        if (IS_ENABLED(CONFIG_KVM) && !is_kernel_in_hyp_mode()) {
                kvm_compute_layout();
                kvm_apply_hyp_relocations();
        }
}

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

void __init smp_prepare_boot_cpu(void)
{
        /*
         * The runtime per-cpu areas have been allocated by
         * setup_per_cpu_areas(), and CPU0's boot time per-cpu area will be
         * freed shortly, so we must move over to the runtime per-cpu area.
         */
        set_my_cpu_offset(per_cpu_offset(smp_processor_id()));

        cpuinfo_store_boot_cpu();
        setup_boot_cpu_features();

        /* Conditionally switch to GIC PMR for interrupt masking */
        if (system_uses_irq_prio_masking())
                init_gic_priority_masking();

        kasan_init_hw_tags();
        /* Init percpu seeds for random tags after cpus are set up. */
        kasan_init_sw_tags();
}

/*
 * 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)
{
        const struct cpu_operations *ops;

        if (init_cpu_ops(cpu))
                return -ENODEV;

        ops = get_cpu_ops(cpu);
        if (ops->cpu_init(cpu))
                return -ENODEV;

        set_cpu_possible(cpu, true);

        return 0;
}

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

int arch_register_cpu(int cpu)
{
        acpi_handle acpi_handle = acpi_get_processor_handle(cpu);
        struct cpu *c = &per_cpu(cpu_devices, cpu);

        if (!acpi_disabled && !acpi_handle &&
            IS_ENABLED(CONFIG_ACPI_HOTPLUG_CPU))
                return -EPROBE_DEFER;

#ifdef CONFIG_ACPI_HOTPLUG_CPU
        /* For now block anything that looks like physical CPU Hotplug */
        if (invalid_logical_cpuid(cpu) || !cpu_present(cpu)) {
                pr_err_once("Changing CPU present bit is not supported\n");
                return -ENODEV;
        }
#endif

        /*
         * Availability of the acpi handle is sufficient to establish
         * that _STA has already been checked. No need to recheck here.
         */
        c->hotpluggable = arch_cpu_is_hotpluggable(cpu);

        return register_cpu(c, cpu);
}

#ifdef CONFIG_ACPI_HOTPLUG_CPU
void arch_unregister_cpu(int cpu)
{
        acpi_handle acpi_handle = acpi_get_processor_handle(cpu);
        struct cpu *c = &per_cpu(cpu_devices, cpu);
        acpi_status status;
        unsigned long long sta;

        if (!acpi_handle) {
                pr_err_once("Removing a CPU without associated ACPI handle\n");
                return;
        }

        status = acpi_evaluate_integer(acpi_handle, "_STA", NULL, &sta);
        if (ACPI_FAILURE(status))
                return;

        /* For now do not allow anything that looks like physical CPU HP */
        if (cpu_present(cpu) && !(sta & ACPI_STA_DEVICE_PRESENT)) {
                pr_err_once("Changing CPU present bit is not supported\n");
                return;
        }

        unregister_cpu(c);
}
#endif /* CONFIG_ACPI_HOTPLUG_CPU */

#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];
}
EXPORT_SYMBOL_GPL(acpi_cpu_get_madt_gicc);

/*
 * 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 | ACPI_MADT_GICC_ONLINE_CAPABLE))) {
                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;
                return;
        }

        if (cpu_count >= NR_CPUS)
                return;

        /* map the logical cpu id to cpu MPIDR */
        set_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);

        cpu_count++;
}

static int __init
acpi_parse_gic_cpu_interface(union acpi_subtable_headers *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->common);

        acpi_map_gic_cpu_interface(processor);

        return 0;
}

static void __init acpi_parse_and_init_cpus(void)
{
        int i;

        /*
         * 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);

        /*
         * In ACPI, SMP and CPU NUMA information is provided in separate
         * static tables, namely the MADT and the SRAT.
         *
         * Thus, it is simpler to first create the cpu logical map through
         * an MADT walk and then map the logical cpus to their node ids
         * as separate steps.
         */
        acpi_map_cpus_to_nodes();

        for (i = 0; i < nr_cpu_ids; i++)
                early_map_cpu_to_node(i, acpi_numa_get_nid(i));
}
#else
#define acpi_parse_and_init_cpus(...)   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_of_cpu_node(dn) {
                u64 hwid = of_get_cpu_hwid(dn, 0);

                if (hwid & ~MPIDR_HWID_BITMASK)
                        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);
                set_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
                acpi_parse_and_init_cpus();

        if (cpu_count > nr_cpu_ids)
                pr_warn("Number of cores (%d) exceeds configured maximum of %u - 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))
                                set_cpu_logical_map(i, INVALID_HWID);
                }
        }
}

void __init smp_prepare_cpus(unsigned int max_cpus)
{
        const struct cpu_operations *ops;
        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);
        numa_add_cpu(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) {

                if (cpu == smp_processor_id())
                        continue;

                ops = get_cpu_ops(cpu);
                if (!ops)
                        continue;

                err = ops->cpu_prepare(cpu);
                if (err)
                        continue;

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

static const char *ipi_types[MAX_IPI] __tracepoint_string = {
        [IPI_RESCHEDULE]        = "Rescheduling interrupts",
        [IPI_CALL_FUNC]         = "Function call interrupts",
        [IPI_CPU_STOP]          = "CPU stop interrupts",
        [IPI_CPU_STOP_NMI]      = "CPU stop NMIs",
        [IPI_TIMER]             = "Timer broadcast interrupts",
        [IPI_IRQ_WORK]          = "IRQ work interrupts",
        [IPI_CPU_BACKTRACE]     = "CPU backtrace interrupts",
        [IPI_KGDB_ROUNDUP]      = "KGDB roundup interrupts",
};

static void smp_cross_call(const struct cpumask *target, unsigned int ipinr);

unsigned long irq_err_count;

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

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

        seq_printf(p, "%*s: %10lu\n", prec, "Err", irq_err_count);
        return 0;
}

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_IRQ_WORK
void arch_irq_work_raise(void)
{
        smp_cross_call(cpumask_of(smp_processor_id()), IPI_IRQ_WORK);
}
#endif

static void __noreturn local_cpu_stop(unsigned int cpu)
{
        set_cpu_online(cpu, false);

        local_daif_mask();
        sdei_mask_local_cpu();
        cpu_park_loop();
}

/*
 * We need to implement panic_smp_self_stop() for parallel panic() calls, so
 * that cpu_online_mask gets correctly updated and smp_send_stop() can skip
 * CPUs that have already stopped themselves.
 */
void __noreturn panic_smp_self_stop(void)
{
        local_cpu_stop(smp_processor_id());
}

static void __noreturn ipi_cpu_crash_stop(unsigned int cpu, struct pt_regs *regs)
{
#ifdef CONFIG_KEXEC_CORE
        /*
         * Use local_daif_mask() instead of local_irq_disable() to make sure
         * that pseudo-NMIs are disabled. The "crash stop" code starts with
         * an IRQ and falls back to NMI (which might be pseudo). If the IRQ
         * finally goes through right as we're timing out then the NMI could
         * interrupt us. It's better to prevent the NMI and let the IRQ
         * finish since the pt_regs will be better.
         */
        local_daif_mask();

        crash_save_cpu(regs, cpu);

        set_cpu_online(cpu, false);

        sdei_mask_local_cpu();

        if (IS_ENABLED(CONFIG_HOTPLUG_CPU))
                __cpu_try_die(cpu);

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

static void arm64_send_ipi(const cpumask_t *mask, unsigned int nr)
{
        unsigned int cpu;

        if (!percpu_ipi_descs)
                __ipi_send_mask(get_ipi_desc(0, nr), mask);
        else
                for_each_cpu(cpu, mask)
                        __ipi_send_single(get_ipi_desc(cpu, nr), cpu);
}

static void arm64_backtrace_ipi(cpumask_t *mask)
{
        arm64_send_ipi(mask, IPI_CPU_BACKTRACE);
}

void arch_trigger_cpumask_backtrace(const cpumask_t *mask, int exclude_cpu)
{
        /*
         * NOTE: though nmi_trigger_cpumask_backtrace() has "nmi_" in the name,
         * nothing about it truly needs to be implemented using an NMI, it's
         * just that it's _allowed_ to work with NMIs. If ipi_should_be_nmi()
         * returned false our backtrace attempt will just use a regular IPI.
         */
        nmi_trigger_cpumask_backtrace(mask, exclude_cpu, arm64_backtrace_ipi);
}

#ifdef CONFIG_KGDB
void kgdb_roundup_cpus(void)
{
        int this_cpu = raw_smp_processor_id();
        int cpu;

        for_each_online_cpu(cpu) {
                /* No need to roundup ourselves */
                if (cpu == this_cpu)
                        continue;

                __ipi_send_single(get_ipi_desc(cpu, IPI_KGDB_ROUNDUP), cpu);
        }
}
#endif

/*
 * Main handler for inter-processor interrupts
 */
static void do_handle_IPI(int ipinr)
{
        unsigned int cpu = smp_processor_id();

        if ((unsigned)ipinr < NR_IPI)
                trace_ipi_entry(ipi_types[ipinr]);

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

        case IPI_CALL_FUNC:
                generic_smp_call_function_interrupt();
                break;

        case IPI_CPU_STOP:
        case IPI_CPU_STOP_NMI:
                if (IS_ENABLED(CONFIG_KEXEC_CORE) && crash_stop) {
                        ipi_cpu_crash_stop(cpu, get_irq_regs());
                        unreachable();
                } else {
                        local_cpu_stop(cpu);
                }
                break;

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

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

        case IPI_CPU_BACKTRACE:
                /*
                 * NOTE: in some cases this _won't_ be NMI context. See the
                 * comment in arch_trigger_cpumask_backtrace().
                 */
                nmi_cpu_backtrace(get_irq_regs());
                break;

        case IPI_KGDB_ROUNDUP:
                kgdb_nmicallback(cpu, get_irq_regs());
                break;

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

        if ((unsigned)ipinr < NR_IPI)
                trace_ipi_exit(ipi_types[ipinr]);
}

static irqreturn_t ipi_handler(int irq, void *data)
{
        unsigned int ipi = (irq - ipi_irq_base) % nr_ipi;

        do_handle_IPI(ipi);
        return IRQ_HANDLED;
}

static void smp_cross_call(const struct cpumask *target, unsigned int ipinr)
{
        trace_ipi_raise(target, ipi_types[ipinr]);
        arm64_send_ipi(target, ipinr);
}

static bool ipi_should_be_nmi(enum ipi_msg_type ipi)
{
        if (!system_uses_irq_prio_masking())
                return false;

        switch (ipi) {
        case IPI_CPU_STOP_NMI:
        case IPI_CPU_BACKTRACE:
        case IPI_KGDB_ROUNDUP:
                return true;
        default:
                return false;
        }
}

static void ipi_setup(int cpu)
{
        int i;

        if (WARN_ON_ONCE(!ipi_irq_base))
                return;

        for (i = 0; i < nr_ipi; i++) {
                if (!percpu_ipi_descs) {
                        if (ipi_should_be_nmi(i)) {
                                prepare_percpu_nmi(ipi_irq_base + i);
                                enable_percpu_nmi(ipi_irq_base + i, 0);
                        } else {
                                enable_percpu_irq(ipi_irq_base + i, 0);
                        }
                } else {
                        enable_irq(irq_desc_get_irq(get_ipi_desc(cpu, i)));
                }
        }
}

#ifdef CONFIG_HOTPLUG_CPU
static void ipi_teardown(int cpu)
{
        int i;

        if (WARN_ON_ONCE(!ipi_irq_base))
                return;

        for (i = 0; i < nr_ipi; i++) {
                if (!percpu_ipi_descs) {
                        if (ipi_should_be_nmi(i)) {
                                disable_percpu_nmi(ipi_irq_base + i);
                                teardown_percpu_nmi(ipi_irq_base + i);
                        } else {
                                disable_percpu_irq(ipi_irq_base + i);
                        }
                } else {
                        disable_irq(irq_desc_get_irq(get_ipi_desc(cpu, i)));
                }
        }
}
#endif

static void ipi_setup_sgi(int ipi)
{
        int err, irq, cpu;

        irq = ipi_irq_base + ipi;

        if (ipi_should_be_nmi(ipi)) {
                err = request_percpu_nmi(irq, ipi_handler, "IPI", NULL, &irq_stat);
                WARN(err, "Could not request IRQ %d as NMI, err=%d\n", irq, err);
        } else {
                err = request_percpu_irq(irq, ipi_handler, "IPI", &irq_stat);
                WARN(err, "Could not request IRQ %d as IRQ, err=%d\n", irq, err);
        }

        for_each_possible_cpu(cpu)
                get_ipi_desc(cpu, ipi) = irq_to_desc(irq);

        irq_set_status_flags(irq, IRQ_HIDDEN);
}

static void ipi_setup_lpi(int ipi, int ncpus)
{
        for (int cpu = 0; cpu < ncpus; cpu++) {
                int err, irq;

                irq = ipi_irq_base + (cpu * nr_ipi) + ipi;

                err = irq_force_affinity(irq, cpumask_of(cpu));
                WARN(err, "Could not force affinity IRQ %d, err=%d\n", irq, err);

                err = request_irq(irq, ipi_handler, IRQF_NO_AUTOEN, "IPI",
                                  NULL);
                WARN(err, "Could not request IRQ %d, err=%d\n", irq, err);

                irq_set_status_flags(irq, (IRQ_HIDDEN | IRQ_NO_BALANCING_MASK));

                get_ipi_desc(cpu, ipi) = irq_to_desc(irq);
        }
}

void __init set_smp_ipi_range_percpu(int ipi_base, int n, int ncpus)
{
        int i;

        WARN_ON(n < MAX_IPI);
        nr_ipi = min(n, MAX_IPI);

        percpu_ipi_descs = !!ncpus;
        ipi_irq_base = ipi_base;

        for (i = 0; i < nr_ipi; i++) {
                if (!percpu_ipi_descs)
                        ipi_setup_sgi(i);
                else
                        ipi_setup_lpi(i, ncpus);
        }

        /* Setup the boot CPU immediately */
        ipi_setup(smp_processor_id());
}

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

#ifdef CONFIG_ARM64_ACPI_PARKING_PROTOCOL
void arch_send_wakeup_ipi(unsigned int cpu)
{
        /*
         * We use a scheduler IPI to wake the CPU as this avoids the need for a
         * dedicated IPI and we can safely handle spurious scheduler IPIs.
         */
        smp_send_reschedule(cpu);
}
#endif

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

/*
 * The number of CPUs online, not counting this CPU (which may not be
 * fully online and so not counted in num_online_cpus()).
 */
static inline unsigned int num_other_online_cpus(void)
{
        unsigned int this_cpu_online = cpu_online(smp_processor_id());

        return num_online_cpus() - this_cpu_online;
}

void smp_send_stop(void)
{
        static unsigned long stop_in_progress;
        static cpumask_t mask;
        unsigned long timeout;

        /*
         * If this cpu is the only one alive at this point in time, online or
         * not, there are no stop messages to be sent around, so just back out.
         */
        if (num_other_online_cpus() == 0)
                goto skip_ipi;

        /* Only proceed if this is the first CPU to reach this code */
        if (test_and_set_bit(0, &stop_in_progress))
                return;

        /*
         * Send an IPI to all currently online CPUs except the CPU running
         * this code.
         *
         * NOTE: we don't do anything here to prevent other CPUs from coming
         * online after we snapshot `cpu_online_mask`. Ideally, the calling code
         * should do something to prevent other CPUs from coming up. This code
         * can be called in the panic path and thus it doesn't seem wise to
         * grab the CPU hotplug mutex ourselves. Worst case:
         * - If a CPU comes online as we're running, we'll likely notice it
         *   during the 1 second wait below and then we'll catch it when we try
         *   with an NMI (assuming NMIs are enabled) since we re-snapshot the
         *   mask before sending an NMI.
         * - If we leave the function and see that CPUs are still online we'll
         *   at least print a warning. Especially without NMIs this function
         *   isn't foolproof anyway so calling code will just have to accept
         *   the fact that there could be cases where a CPU can't be stopped.
         */
        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");

        /*
         * Start with a normal IPI and wait up to one second for other CPUs to
         * stop. We do this first because it gives other processors a chance
         * to exit critical sections / drop locks and makes the rest of the
         * stop process (especially console flush) more robust.
         */
        smp_cross_call(&mask, IPI_CPU_STOP);
        timeout = USEC_PER_SEC;
        while (num_other_online_cpus() && timeout--)
                udelay(1);

        /*
         * If CPUs are still online, try an NMI. There's no excuse for this to
         * be slow, so we only give them an extra 10 ms to respond.
         */
        if (num_other_online_cpus() && ipi_should_be_nmi(IPI_CPU_STOP_NMI)) {
                smp_rmb();
                cpumask_copy(&mask, cpu_online_mask);
                cpumask_clear_cpu(smp_processor_id(), &mask);

                pr_info("SMP: retry stop with NMI for CPUs %*pbl\n",
                        cpumask_pr_args(&mask));

                smp_cross_call(&mask, IPI_CPU_STOP_NMI);
                timeout = USEC_PER_MSEC * 10;
                while (num_other_online_cpus() && timeout--)
                        udelay(1);
        }

        if (num_other_online_cpus()) {
                smp_rmb();
                cpumask_copy(&mask, cpu_online_mask);
                cpumask_clear_cpu(smp_processor_id(), &mask);

                pr_warn("SMP: failed to stop secondary CPUs %*pbl\n",
                        cpumask_pr_args(&mask));
        }

skip_ipi:
        sdei_mask_local_cpu();
}

#ifdef CONFIG_KEXEC_CORE
void crash_smp_send_stop(void)
{
        /*
         * This function can be called twice in panic path, but obviously
         * we execute this only once.
         *
         * We use this same boolean to tell whether the IPI we send was a
         * stop or a "crash stop".
         */
        if (crash_stop)
                return;
        crash_stop = 1;

        smp_send_stop();

        sdei_handler_abort();
}

bool smp_crash_stop_failed(void)
{
        return num_other_online_cpus() != 0;
}
#endif

static bool have_cpu_die(void)
{
#ifdef CONFIG_HOTPLUG_CPU
        int any_cpu = raw_smp_processor_id();
        const struct cpu_operations *ops = get_cpu_ops(any_cpu);

        if (ops && ops->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 ||
                is_protected_kvm_enabled();
}