KVM: arm/arm64: implement kvm_arm_[halt,resume]_guest

We introduce kvm_arm_halt_guest and resume functions. They
will be used for IRQ forward state change.

Halt is synchronous and prevents the guest from being re-entered.
We use the same mechanism put in place for PSCI former pause,
now renamed power_off. A new flag is introduced in arch vcpu state,
pause, only meant to be used by those functions.

Signed-off-by: Eric Auger <[e-mail]>
Reviewed-by: Christoffer Dall <[e-mail]>
Signed-off-by: Christoffer Dall <[e-mail]>

arch/arm/include/asm/kvm_host.h

···
 	/* vcpu power-off state */
 	bool power_off;
 
+	 /* Don't run the guest (internal implementation need) */
+	bool pause;
+
 	/* IO related fields */
 	struct kvm_decode mmio_decode;
 

arch/arm/kvm/arm.c

···
 int kvm_arch_vcpu_runnable(struct kvm_vcpu *v)
 {
 	return ((!!v->arch.irq_lines || kvm_vgic_vcpu_pending_irq(v))
-		&& !v->arch.power_off);
+		&& !v->arch.power_off && !v->arch.pause);
 }
 
 /* Just ensure a guest exit from a particular CPU */
···
 	return vgic_initialized(kvm);
 }
 
+static void kvm_arm_halt_guest(struct kvm *kvm) __maybe_unused;
+static void kvm_arm_resume_guest(struct kvm *kvm) __maybe_unused;
+
+static void kvm_arm_halt_guest(struct kvm *kvm)
+{
+	int i;
+	struct kvm_vcpu *vcpu;
+
+	kvm_for_each_vcpu(i, vcpu, kvm)
+		vcpu->arch.pause = true;
+	force_vm_exit(cpu_all_mask);
+}
+
+static void kvm_arm_resume_guest(struct kvm *kvm)
+{
+	int i;
+	struct kvm_vcpu *vcpu;
+
+	kvm_for_each_vcpu(i, vcpu, kvm) {
+		wait_queue_head_t *wq = kvm_arch_vcpu_wq(vcpu);
+
+		vcpu->arch.pause = false;
+		wake_up_interruptible(wq);
+	}
+}
+
 static void vcpu_sleep(struct kvm_vcpu *vcpu)
 {
 	wait_queue_head_t *wq = kvm_arch_vcpu_wq(vcpu);
 
-	wait_event_interruptible(*wq, !vcpu->arch.power_off);
+	wait_event_interruptible(*wq, ((!vcpu->arch.power_off) &&
+				       (!vcpu->arch.pause)));
 }
 
 static int kvm_vcpu_initialized(struct kvm_vcpu *vcpu)
···
 
 		update_vttbr(vcpu->kvm);
 
-		if (vcpu->arch.power_off)
+		if (vcpu->arch.power_off || vcpu->arch.pause)
 			vcpu_sleep(vcpu);
 
 		/*
···
 		}
 
 		if (ret <= 0 || need_new_vmid_gen(vcpu->kvm) ||
-			vcpu->arch.power_off) {
+			vcpu->arch.power_off || vcpu->arch.pause) {
 			local_irq_enable();
 			kvm_timer_sync_hwstate(vcpu);
 			kvm_vgic_sync_hwstate(vcpu);

arch/arm64/include/asm/kvm_host.h

···
 	/* vcpu power-off state */
 	bool power_off;
 
+	/* Don't run the guest (internal implementation need) */
+	bool pause;
+
 	/* IO related fields */
 	struct kvm_decode mmio_decode;