// SPDX-License-Identifier: GPL-2.0
/*
 * Generic cpu hotunplug interrupt migration code copied from the
 * arch/arm implementation
 *
 * Copyright (C) Russell King
 *
 * 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.
 */
#include <linux/interrupt.h>
#include <linux/ratelimit.h>
#include <linux/irq.h>
#include <linux/sched/isolation.h>

#include "internals.h"

/* For !GENERIC_IRQ_EFFECTIVE_AFF_MASK this looks at general affinity mask */
static inline bool irq_needs_fixup(struct irq_data *d)
{
        const struct cpumask *m = irq_data_get_effective_affinity_mask(d);
        unsigned int cpu = smp_processor_id();

#ifdef CONFIG_GENERIC_IRQ_EFFECTIVE_AFF_MASK
        /*
         * The cpumask_empty() check is a workaround for interrupt chips,
         * which do not implement effective affinity, but the architecture has
         * enabled the config switch. Use the general affinity mask instead.
         */
        if (cpumask_empty(m))
                m = irq_data_get_affinity_mask(d);

        /*
         * Sanity check. If the mask is not empty when excluding the outgoing
         * CPU then it must contain at least one online CPU. The outgoing CPU
         * has been removed from the online mask already.
         */
        if (cpumask_any_but(m, cpu) < nr_cpu_ids &&
            cpumask_any_and(m, cpu_online_mask) >= nr_cpu_ids) {
                /*
                 * If this happens then there was a missed IRQ fixup at some
                 * point. Warn about it and enforce fixup.
                 */
                pr_warn("Eff. affinity %*pbl of IRQ %u contains only offline CPUs after offlining CPU %u\n",
                        cpumask_pr_args(m), d->irq, cpu);
                return true;
        }
#endif
        return cpumask_test_cpu(cpu, m);
}

static bool migrate_one_irq(struct irq_desc *desc)
{
        struct irq_data *d = irq_desc_get_irq_data(desc);
        struct irq_chip *chip = irq_data_get_irq_chip(d);
        bool maskchip = !irq_can_move_pcntxt(d) && !irqd_irq_masked(d);
        const struct cpumask *affinity;
        bool brokeaff = false;
        int err;

        /*
         * IRQ chip might be already torn down, but the irq descriptor is
         * still in the radix tree. Also if the chip has no affinity setter,
         * nothing can be done here.
         */
        if (!chip || !chip->irq_set_affinity) {
                pr_debug("IRQ %u: Unable to migrate away\n", d->irq);
                return false;
        }

        /*
         * No move required, if:
         * - Interrupt is per cpu
         * - Interrupt is not started
         * - Affinity mask does not include this CPU.
         *
         * Note: Do not check desc->action as this might be a chained
         * interrupt.
         */
        if (irqd_is_per_cpu(d) || !irqd_is_started(d) || !irq_needs_fixup(d)) {
                /*
                 * If an irq move is pending, abort it if the dying CPU is
                 * the sole target.
                 */
                irq_fixup_move_pending(desc, false);
                return false;
        }

        /*
         * Complete an eventually pending irq move cleanup. If this
         * interrupt was moved in hard irq context, then the vectors need
         * to be cleaned up. It can't wait until this interrupt actually
         * happens and this CPU was involved.
         */
        irq_force_complete_move(desc);

        /*
         * If there is a setaffinity pending, then try to reuse the pending
         * mask, so the last change of the affinity does not get lost. If
         * there is no move pending or the pending mask does not contain
         * any online CPU, use the current affinity mask.
         */
        if (irq_fixup_move_pending(desc, true))
                affinity = irq_desc_get_pending_mask(desc);
        else
                affinity = irq_data_get_affinity_mask(d);

        /* Mask the chip for interrupts which cannot move in process context */
        if (maskchip && chip->irq_mask)
                chip->irq_mask(d);

        if (cpumask_any_and(affinity, cpu_online_mask) >= nr_cpu_ids) {
                /*
                 * If the interrupt is managed, then shut it down and leave
                 * the affinity untouched.
                 */
                if (irqd_affinity_is_managed(d)) {
                        irqd_set_managed_shutdown(d);
                        irq_shutdown_and_deactivate(desc);
                        return false;
                }
                affinity = cpu_online_mask;
                brokeaff = true;
        }
        /*
         * Do not set the force argument of irq_do_set_affinity() as this
         * disables the masking of offline CPUs from the supplied affinity
         * mask and therefore might keep/reassign the irq to the outgoing
         * CPU.
         */
        err = irq_do_set_affinity(d, affinity, false);
        if (err) {
                pr_warn_ratelimited("IRQ%u: set affinity failed(%d).\n",
                                    d->irq, err);
                brokeaff = false;
        }

        if (maskchip && chip->irq_unmask)
                chip->irq_unmask(d);

        return brokeaff;
}

/**
 * irq_migrate_all_off_this_cpu - Migrate irqs away from offline cpu
 *
 * The current CPU has been marked offline.  Migrate IRQs off this CPU.
 * If the affinity settings do not allow other CPUs, force them onto any
 * available CPU.
 *
 * Note: we must iterate over all IRQs, whether they have an attached
 * action structure or not, as we need to get chained interrupts too.
 */
void irq_migrate_all_off_this_cpu(void)
{
        struct irq_desc *desc;
        unsigned int irq;

        for_each_active_irq(irq) {
                bool affinity_broken;

                desc = irq_to_desc(irq);
                raw_spin_lock(&desc->lock);
                affinity_broken = migrate_one_irq(desc);
                raw_spin_unlock(&desc->lock);

                if (affinity_broken) {
                        pr_debug_ratelimited("IRQ %u: no longer affine to CPU%u\n",
                                            irq, smp_processor_id());
                }
        }
}

static bool hk_should_isolate(struct irq_data *data, unsigned int cpu)
{
        const struct cpumask *hk_mask;

        if (!housekeeping_enabled(HK_FLAG_MANAGED_IRQ))
                return false;

        hk_mask = housekeeping_cpumask(HK_FLAG_MANAGED_IRQ);
        if (cpumask_subset(irq_data_get_effective_affinity_mask(data), hk_mask))
                return false;

        return cpumask_test_cpu(cpu, hk_mask);
}

static void irq_restore_affinity_of_irq(struct irq_desc *desc, unsigned int cpu)
{
        struct irq_data *data = irq_desc_get_irq_data(desc);
        const struct cpumask *affinity = irq_data_get_affinity_mask(data);

        if (!irqd_affinity_is_managed(data) || !desc->action ||
            !irq_data_get_irq_chip(data) || !cpumask_test_cpu(cpu, affinity))
                return;

        if (irqd_is_managed_and_shutdown(data)) {
                irq_startup(desc, IRQ_RESEND, IRQ_START_COND);
                return;
        }

        /*
         * If the interrupt can only be directed to a single target
         * CPU then it is already assigned to a CPU in the affinity
         * mask. No point in trying to move it around unless the
         * isolation mechanism requests to move it to an upcoming
         * housekeeping CPU.
         */
        if (!irqd_is_single_target(data) || hk_should_isolate(data, cpu))
                irq_set_affinity_locked(data, affinity, false);
}

/**
 * irq_affinity_online_cpu - Restore affinity for managed interrupts
 * @cpu:        Upcoming CPU for which interrupts should be restored
 */
int irq_affinity_online_cpu(unsigned int cpu)
{
        struct irq_desc *desc;
        unsigned int irq;

        irq_lock_sparse();
        for_each_active_irq(irq) {
                desc = irq_to_desc(irq);
                raw_spin_lock_irq(&desc->lock);
                irq_restore_affinity_of_irq(desc, cpu);
                raw_spin_unlock_irq(&desc->lock);
        }
        irq_unlock_sparse();

        return 0;
}