kvm: destroy emulated devices on VM exit

The hassle of getting refcounting right was greater than the hassle
of keeping a list of devices to destroy on VM exit.
Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Alexander Graf <agraf@suse.de>

arch/powerpc/kvm/mpic.c

@@ -1781,7 +1781,6 @@ int kvmppc_mpic_connect_vcpu(struct kvm_device *dev, struct kvm_vcpu *vcpu,
 	if (opp->mpic_mode_mask == GCR_MODE_PROXY)
 		vcpu->arch.epr_flags |= KVMPPC_EPR_KERNEL;
 
-	kvm_device_get(dev);
 out:
 	spin_unlock_irq(&opp->lock);
 	return ret;
@@ -1797,7 +1796,6 @@ void kvmppc_mpic_disconnect_vcpu(struct openpic *opp, struct kvm_vcpu *vcpu)
 	BUG_ON(!opp->dst[vcpu->arch.irq_cpu_id].vcpu);
 
 	opp->dst[vcpu->arch.irq_cpu_id].vcpu = NULL;
-	kvm_device_put(opp->dev);
 }
 
 /*

include/linux/kvm_host.h

@@ -393,6 +393,7 @@ struct kvm {
 	long mmu_notifier_count;
 #endif
 	long tlbs_dirty;
+	struct list_head devices;
 };
 
 #define kvm_err(fmt, ...) \
@@ -1069,8 +1070,8 @@ struct kvm_device_ops;
 struct kvm_device {
 	struct kvm_device_ops *ops;
 	struct kvm *kvm;
-	atomic_t users;
 	void *private;
+	struct list_head vm_node;
 };
 
 /* create, destroy, and name are mandatory */

virt/kvm/kvm_main.c

@@ -504,6 +504,7 @@ static struct kvm *kvm_create_vm(unsigned long type)
 	mutex_init(&kvm->irq_lock);
 	mutex_init(&kvm->slots_lock);
 	atomic_set(&kvm->users_count, 1);
+	INIT_LIST_HEAD(&kvm->devices);
 
 	r = kvm_init_mmu_notifier(kvm);
 	if (r)
@@ -581,6 +582,19 @@ void kvm_free_physmem(struct kvm *kvm)
 	kfree(kvm->memslots);
 }
 
+static void kvm_destroy_devices(struct kvm *kvm)
+{
+	struct list_head *node, *tmp;
+
+	list_for_each_safe(node, tmp, &kvm->devices) {
+		struct kvm_device *dev =
+			list_entry(node, struct kvm_device, vm_node);
+
+		list_del(node);
+		dev->ops->destroy(dev);
+	}
+}
+
 static void kvm_destroy_vm(struct kvm *kvm)
 {
 	int i;
@@ -600,6 +614,7 @@ static void kvm_destroy_vm(struct kvm *kvm)
 	kvm_arch_flush_shadow_all(kvm);
 #endif
 	kvm_arch_destroy_vm(kvm);
+	kvm_destroy_devices(kvm);
 	kvm_free_physmem(kvm);
 	cleanup_srcu_struct(&kvm->srcu);
 	kvm_arch_free_vm(kvm);
@@ -2195,23 +2210,11 @@ static long kvm_device_ioctl(struct file *filp, unsigned int ioctl,
 	}
 }
 
-void kvm_device_get(struct kvm_device *dev)
-{
-	atomic_inc(&dev->users);
-}
-
-void kvm_device_put(struct kvm_device *dev)
-{
-	if (atomic_dec_and_test(&dev->users))
-		dev->ops->destroy(dev);
-}
-
 static int kvm_device_release(struct inode *inode, struct file *filp)
 {
 	struct kvm_device *dev = filp->private_data;
 	struct kvm *kvm = dev->kvm;
 
-	kvm_device_put(dev);
 	kvm_put_kvm(kvm);
 	return 0;
 }
@@ -2257,7 +2260,6 @@ static int kvm_ioctl_create_device(struct kvm *kvm,
 
 	dev->ops = ops;
 	dev->kvm = kvm;
-	atomic_set(&dev->users, 1);
 
 	ret = ops->create(dev, cd->type);
 	if (ret < 0) {
@@ -2271,6 +2273,7 @@ static int kvm_ioctl_create_device(struct kvm *kvm,
 		return ret;
 	}
 
+	list_add(&dev->vm_node, &kvm->devices);
 	kvm_get_kvm(kvm);
 	cd->fd = ret;
 	return 0;