kvm hypervisor: Simplify kvm_for_each_vcpu with kvm_irq_delivery_to_apic

Note that we are using APIC_DM_REMRD which has reserved usage.
In future if APIC_DM_REMRD usage is standardized, then we should
find some other way or go back to old method.

Suggested-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Acked-by: Gleb Natapov <gleb@redhat.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Gleb Natapov <gleb@redhat.com>

arch/x86/kvm/lapic.c

@@ -689,7 +689,10 @@ static int __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
 		break;
 
 	case APIC_DM_REMRD:
-		apic_debug("Ignoring delivery mode 3\n");
+		result = 1;
+		vcpu->arch.pv.pv_unhalted = 1;
+		kvm_make_request(KVM_REQ_EVENT, vcpu);
+		kvm_vcpu_kick(vcpu);
 		break;
 
 	case APIC_DM_SMI:

arch/x86/kvm/x86.c

@@ -5595,27 +5595,14 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
  */
 static void kvm_pv_kick_cpu_op(struct kvm *kvm, unsigned long flags, int apicid)
 {
-	struct kvm_vcpu *vcpu = NULL;
-	int i;
+	struct kvm_lapic_irq lapic_irq;
 
-	kvm_for_each_vcpu(i, vcpu, kvm) {
-		if (!kvm_apic_present(vcpu))
-			continue;
+	lapic_irq.shorthand = 0;
+	lapic_irq.dest_mode = 0;
+	lapic_irq.dest_id = apicid;
 
-		if (kvm_apic_match_dest(vcpu, 0, 0, apicid, 0))
-			break;
-	}
-	if (vcpu) {
-		/*
-		 * Setting unhalt flag here can result in spurious runnable
-		 * state when unhalt reset does not happen in vcpu_block.
-		 * But that is harmless since that should soon result in halt.
-		 */
-		vcpu->arch.pv.pv_unhalted = true;
-		/* We need everybody see unhalt before vcpu unblocks */
-		smp_wmb();
-		kvm_vcpu_kick(vcpu);
-	}
+	lapic_irq.delivery_mode = APIC_DM_REMRD;
+	kvm_irq_delivery_to_apic(kvm, 0, &lapic_irq, NULL);
 }
 
 int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)