// SPDX-License-Identifier: GPL-2.0
#include <linux/export.h>
#include <linux/types.h>
#include <linux/interrupt.h>
#include <linux/jump_label.h>
#include <linux/kvm_para.h>
#include <linux/static_call.h>
#include <asm/paravirt.h>

struct static_key paravirt_steal_enabled;
struct static_key paravirt_steal_rq_enabled;

static u64 native_steal_clock(int cpu)
{
	return 0;
}

DEFINE_STATIC_CALL(pv_steal_clock, native_steal_clock);

#ifdef CONFIG_SMP
static void pv_send_ipi_single(int cpu, unsigned int action)
{
	int min, old;
	irq_cpustat_t *info = &per_cpu(irq_stat, cpu);

	old = atomic_fetch_or(BIT(action), &info->message);
	if (old)
		return;

	min = cpu_logical_map(cpu);
	kvm_hypercall3(KVM_HCALL_FUNC_IPI, 1, 0, min);
}

#define KVM_IPI_CLUSTER_SIZE	(2 * BITS_PER_LONG)

static void pv_send_ipi_mask(const struct cpumask *mask, unsigned int action)
{
	int i, cpu, min = 0, max = 0, old;
	__uint128_t bitmap = 0;
	irq_cpustat_t *info;

	if (cpumask_empty(mask))
		return;

	action = BIT(action);
	for_each_cpu(i, mask) {
		info = &per_cpu(irq_stat, i);
		old = atomic_fetch_or(action, &info->message);
		if (old)
			continue;

		cpu = cpu_logical_map(i);
		if (!bitmap) {
			min = max = cpu;
		} else if (cpu < min && cpu > (max - KVM_IPI_CLUSTER_SIZE)) {
			/* cpu < min, and bitmap still enough */
			bitmap <<= min - cpu;
			min = cpu;
		} else if (cpu > min && cpu < (min + KVM_IPI_CLUSTER_SIZE)) {
			/* cpu > min, and bitmap still enough */
			max = cpu > max ? cpu : max;
		} else {
			/*
			 * With cpu, bitmap will exceed KVM_IPI_CLUSTER_SIZE,
			 * send IPI here directly and skip the remaining CPUs.
			 */
			kvm_hypercall3(KVM_HCALL_FUNC_IPI, (unsigned long)bitmap,
				      (unsigned long)(bitmap >> BITS_PER_LONG), min);
			min = max = cpu;
			bitmap = 0;
		}
		__set_bit(cpu - min, (unsigned long *)&bitmap);
	}

	if (bitmap)
		kvm_hypercall3(KVM_HCALL_FUNC_IPI, (unsigned long)bitmap,
			      (unsigned long)(bitmap >> BITS_PER_LONG), min);
}

static irqreturn_t pv_ipi_interrupt(int irq, void *dev)
{
	u32 action;
	irq_cpustat_t *info;

	/* Clear SWI interrupt */
	clear_csr_estat(1 << INT_SWI0);
	info = this_cpu_ptr(&irq_stat);
	action = atomic_xchg(&info->message, 0);

	if (action & SMP_RESCHEDULE) {
		scheduler_ipi();
		info->ipi_irqs[IPI_RESCHEDULE]++;
	}

	if (action & SMP_CALL_FUNCTION) {
		generic_smp_call_function_interrupt();
		info->ipi_irqs[IPI_CALL_FUNCTION]++;
	}

	return IRQ_HANDLED;
}

static void pv_init_ipi(void)
{
	int r, swi;

	swi = get_percpu_irq(INT_SWI0);
	if (swi < 0)
		panic("SWI0 IRQ mapping failed\n");
	irq_set_percpu_devid(swi);
	r = request_percpu_irq(swi, pv_ipi_interrupt, "SWI0-IPI", &irq_stat);
	if (r < 0)
		panic("SWI0 IRQ request failed\n");
}
#endif

static bool kvm_para_available(void)
{
	int config;
	static int hypervisor_type;

	if (!hypervisor_type) {
		config = read_cpucfg(CPUCFG_KVM_SIG);
		if (!memcmp(&config, KVM_SIGNATURE, 4))
			hypervisor_type = HYPERVISOR_KVM;
	}

	return hypervisor_type == HYPERVISOR_KVM;
}

int __init pv_ipi_init(void)
{
	int feature;

	if (!cpu_has_hypervisor)
		return 0;
	if (!kvm_para_available())
		return 0;

	feature = read_cpucfg(CPUCFG_KVM_FEATURE);
	if (!(feature & KVM_FEATURE_IPI))
		return 0;

#ifdef CONFIG_SMP
	mp_ops.init_ipi		= pv_init_ipi;
	mp_ops.send_ipi_single	= pv_send_ipi_single;
	mp_ops.send_ipi_mask	= pv_send_ipi_mask;
#endif

	return 0;
}