static void kvm_sched_yield(struct kvm_vcpu *vcpu, unsigned long dest_id)
{
	struct kvm_vcpu *target = NULL;
	struct kvm_apic_map *map;

	vcpu->stat.directed_yield_attempted++;

	if (single_task_running())
		goto no_yield;

	rcu_read_lock();
	map = rcu_dereference(vcpu->kvm->arch.apic_map);

	if (likely(map) && dest_id <= map->max_apic_id && map->phys_map[dest_id])
		target = map->phys_map[dest_id]->vcpu;

	rcu_read_unlock();

	if (!target || !READ_ONCE(target->ready))
		goto no_yield;

	/* Ignore requests to yield to self */
	if (vcpu == target)
		goto no_yield;

	if (kvm_vcpu_yield_to(target) <= 0)
		goto no_yield;

	vcpu->stat.directed_yield_successful++;

no_yield:
	return;
}
static void kvm_sched_yield(struct kvm_vcpu *vcpu, unsigned long dest_id)
{
	struct kvm_vcpu *target = NULL;
	struct kvm_apic_map *map;

	vcpu->stat.directed_yield_attempted++;

	if (single_task_running())
		goto no_yield;

	rcu_read_lock();
	map = rcu_dereference(vcpu->kvm->arch.apic_map);

	if (likely(map) && dest_id <= map->max_apic_id && map->phys_map[dest_id])
		target = map->phys_map[dest_id]->vcpu;

	rcu_read_unlock();

	if (!target || !READ_ONCE(target->ready))
		goto no_yield;

	 
	if (vcpu == target)
		goto no_yield;

	if (kvm_vcpu_yield_to(target) <= 0)
		goto no_yield;

	vcpu->stat.directed_yield_successful++;

no_yield:
	return;
}