// SPDX-License-Identifier: GPL-2.0
/*
 * Split spinlock implementation out into its own file, so it can be
 * compiled in a FTRACE-compatible way.
 */
#include <linux/kernel.h>
#include <linux/spinlock.h>
#include <linux/slab.h>
#include <linux/atomic.h>

#include <asm/qspinlock.h>

#include <xen/events.h>

#include "xen-ops.h"

static DEFINE_PER_CPU(int, lock_kicker_irq) = -1;
static DEFINE_PER_CPU(char *, irq_name);
static DEFINE_PER_CPU(atomic_t, xen_qlock_wait_nest);

static void xen_qlock_kick(int cpu)
{
        int irq = per_cpu(lock_kicker_irq, cpu);

        /* Don't kick if the target's kicker interrupt is not initialized. */
        if (irq == -1)
                return;

        xen_send_IPI_one(cpu, XEN_SPIN_UNLOCK_VECTOR);
}

/*
 * Halt the current CPU & release it back to the host
 */
static void xen_qlock_wait(u8 *byte, u8 val)
{
        int irq = __this_cpu_read(lock_kicker_irq);
        atomic_t *nest_cnt = this_cpu_ptr(&xen_qlock_wait_nest);

        /* If kicker interrupts not initialized yet, just spin */
        if (irq == -1 || in_nmi())
                return;

        /* Detect reentry. */
        atomic_inc(nest_cnt);

        /* If irq pending already and no nested call clear it. */
        if (atomic_read(nest_cnt) == 1 && xen_test_irq_pending(irq)) {
                xen_clear_irq_pending(irq);
        } else if (READ_ONCE(*byte) == val) {
                /* Block until irq becomes pending (or a spurious wakeup) */
                xen_poll_irq(irq);
        }

        atomic_dec(nest_cnt);
}

static irqreturn_t dummy_handler(int irq, void *dev_id)
{
        BUG();
        return IRQ_HANDLED;
}

void xen_init_lock_cpu(int cpu)
{
        int irq;
        char *name;

        if (nopvspin)
                return;

        WARN(per_cpu(lock_kicker_irq, cpu) >= 0, "spinlock on CPU%d exists on IRQ%d!\n",
             cpu, per_cpu(lock_kicker_irq, cpu));

        name = kasprintf(GFP_KERNEL, "spinlock%d", cpu);
        per_cpu(irq_name, cpu) = name;
        irq = bind_ipi_to_irqhandler(XEN_SPIN_UNLOCK_VECTOR,
                                     cpu,
                                     dummy_handler,
                                     IRQF_PERCPU|IRQF_NOBALANCING,
                                     name,
                                     NULL);

        if (irq >= 0) {
                disable_irq(irq); /* make sure it's never delivered */
                per_cpu(lock_kicker_irq, cpu) = irq;
        }

        printk("cpu %d spinlock event irq %d\n", cpu, irq);
}

void xen_uninit_lock_cpu(int cpu)
{
        int irq;

        if (nopvspin)
                return;

        kfree(per_cpu(irq_name, cpu));
        per_cpu(irq_name, cpu) = NULL;
        /*
         * When booting the kernel with 'mitigations=auto,nosmt', the secondary
         * CPUs are not activated, and lock_kicker_irq is not initialized.
         */
        irq = per_cpu(lock_kicker_irq, cpu);
        if (irq == -1)
                return;

        unbind_from_irqhandler(irq, NULL);
        per_cpu(lock_kicker_irq, cpu) = -1;
}

PV_CALLEE_SAVE_REGS_THUNK(xen_vcpu_stolen);

/*
 * Our init of PV spinlocks is split in two init functions due to us
 * using paravirt patching and jump labels patching and having to do
 * all of this before SMP code is invoked.
 *
 * The paravirt patching needs to be done _before_ the alternative asm code
 * is started, otherwise we would not patch the core kernel code.
 */
void __init xen_init_spinlocks(void)
{
        /*  Don't need to use pvqspinlock code if there is only 1 vCPU. */
        if (num_possible_cpus() == 1)
                nopvspin = true;

        if (nopvspin) {
                printk(KERN_DEBUG "xen: PV spinlocks disabled\n");
                static_branch_disable(&virt_spin_lock_key);
                return;
        }
        printk(KERN_DEBUG "xen: PV spinlocks enabled\n");

        __pv_init_lock_hash();
        pv_ops_lock.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath;
        pv_ops_lock.queued_spin_unlock =
                PV_CALLEE_SAVE(__pv_queued_spin_unlock);
        pv_ops_lock.wait = xen_qlock_wait;
        pv_ops_lock.kick = xen_qlock_kick;
        pv_ops_lock.vcpu_is_preempted = PV_CALLEE_SAVE(xen_vcpu_stolen);
}