diff --git a/Documentation/driver-api/vfio-mediated-device.rst b/Documentation/driver-api/vfio-mediated-device.rst
index f410a1cd98bb06..a4f7f1362fa8a5 100644
--- a/Documentation/driver-api/vfio-mediated-device.rst
+++ b/Documentation/driver-api/vfio-mediated-device.rst
@@ -106,6 +106,7 @@ structure to represent a mediated device's driver::
 	     int  (*probe)  (struct mdev_device *dev);
 	     void (*remove) (struct mdev_device *dev);
 	     struct device_driver    driver;
+	     unsigned int (*get_available)(struct mdev_type *mtype);
      };
 
 A mediated bus driver for mdev should use this structure in the function calls
@@ -232,7 +233,8 @@ Directories and files under the sysfs for Each Physical Device
 * available_instances
 
   This attribute should show the number of devices of type <type-id> that can be
-  created.
+  created. Drivers can supply a get_available() function pointer to have the
+  core code create and maintain this sysfs automatically.
 
 * [device]
 
diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c
index 769edbbd164313..df9e1e265bca1a 100644
--- a/drivers/s390/cio/vfio_ccw_drv.c
+++ b/drivers/s390/cio/vfio_ccw_drv.c
@@ -106,7 +106,6 @@ static struct vfio_ccw_private *vfio_ccw_alloc_private(struct subchannel *sch)
 	INIT_LIST_HEAD(&private->crw);
 	INIT_WORK(&private->io_work, vfio_ccw_sch_io_todo);
 	INIT_WORK(&private->crw_work, vfio_ccw_crw_todo);
-	atomic_set(&private->avail, 1);
 
 	private->cp.guest_cp = kcalloc(CCWCHAIN_LEN_MAX, sizeof(struct ccw1),
 				       GFP_KERNEL);
diff --git a/drivers/s390/cio/vfio_ccw_ops.c b/drivers/s390/cio/vfio_ccw_ops.c
index a7f642be9c8898..97df5c711736c4 100644
--- a/drivers/s390/cio/vfio_ccw_ops.c
+++ b/drivers/s390/cio/vfio_ccw_ops.c
@@ -70,20 +70,9 @@ static ssize_t name_show(struct mdev_type *mtype,
 }
 static MDEV_TYPE_ATTR_RO(name);
 
-static ssize_t available_instances_show(struct mdev_type *mtype,
-					struct mdev_type_attribute *attr,
-					char *buf)
-{
-	struct vfio_ccw_private *private =
-		dev_get_drvdata(mtype_get_parent_dev(mtype));
-
-	return sprintf(buf, "%d\n", atomic_read(&private->avail));
-}
-static MDEV_TYPE_ATTR_RO(available_instances);
 
 static struct attribute *mdev_types_attrs[] = {
 	&mdev_type_attr_name.attr,
-	&mdev_type_attr_available_instances.attr,
 	NULL,
 };
 
@@ -102,9 +91,6 @@ static int vfio_ccw_mdev_probe(struct mdev_device *mdev)
 	struct vfio_ccw_private *private = dev_get_drvdata(mdev->dev.parent);
 	int ret;
 
-	if (atomic_dec_if_positive(&private->avail) < 0)
-		return -EPERM;
-
 	memset(&private->vdev, 0, sizeof(private->vdev));
 	vfio_init_group_dev(&private->vdev, &mdev->dev,
 			    &vfio_ccw_dev_ops);
@@ -118,13 +104,12 @@ static int vfio_ccw_mdev_probe(struct mdev_device *mdev)
 
 	ret = vfio_register_emulated_iommu_dev(&private->vdev);
 	if (ret)
-		goto err_atomic;
+		goto err_init;
 	dev_set_drvdata(&mdev->dev, private);
 	return 0;
 
-err_atomic:
+err_init:
 	vfio_uninit_group_dev(&private->vdev);
-	atomic_inc(&private->avail);
 	private->mdev = NULL;
 	return ret;
 }
@@ -141,7 +126,6 @@ static void vfio_ccw_mdev_remove(struct mdev_device *mdev)
 	vfio_unregister_group_dev(&private->vdev);
 	vfio_uninit_group_dev(&private->vdev);
 	private->mdev = NULL;
-	atomic_inc(&private->avail);
 }
 
 static int vfio_ccw_mdev_open_device(struct vfio_device *vdev)
@@ -610,6 +594,11 @@ static void vfio_ccw_mdev_request(struct vfio_device *vdev, unsigned int count)
 	}
 }
 
+static unsigned int vfio_ccw_get_available(struct mdev_type *mtype)
+{
+	return 1;
+}
+
 static const struct vfio_device_ops vfio_ccw_dev_ops = {
 	.open_device = vfio_ccw_mdev_open_device,
 	.close_device = vfio_ccw_mdev_close_device,
@@ -627,6 +616,7 @@ struct mdev_driver vfio_ccw_mdev_driver = {
 	},
 	.probe = vfio_ccw_mdev_probe,
 	.remove = vfio_ccw_mdev_remove,
+	.get_available = vfio_ccw_get_available,
 };
 
 static const struct mdev_parent_ops vfio_ccw_mdev_ops = {
diff --git a/drivers/s390/cio/vfio_ccw_private.h b/drivers/s390/cio/vfio_ccw_private.h
index 5e98eacdf31074..bbc97eb9d9c6fc 100644
--- a/drivers/s390/cio/vfio_ccw_private.h
+++ b/drivers/s390/cio/vfio_ccw_private.h
@@ -72,7 +72,6 @@ struct vfio_ccw_crw {
  * @sch: pointer to the subchannel
  * @state: internal state of the device
  * @completion: synchronization helper of the I/O completion
- * @avail: available for creating a mediated device
  * @mdev: pointer to the mediated device
  * @nb: notifier for vfio events
  * @io_region: MMIO region to input/output I/O arguments/results
@@ -96,7 +95,6 @@ struct vfio_ccw_private {
 	struct subchannel	*sch;
 	int			state;
 	struct completion	*completion;
-	atomic_t		avail;
 	struct mdev_device	*mdev;
 	struct notifier_block	nb;
 	struct ccw_io_region	*io_region;
diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index f80246b30aff30..b6eaee24f798a8 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -333,14 +333,9 @@ static int vfio_ap_mdev_probe(struct mdev_device *mdev)
 	struct ap_matrix_mdev *matrix_mdev;
 	int ret;
 
-	if ((atomic_dec_if_positive(&matrix_dev->available_instances) < 0))
-		return -EPERM;
-
 	matrix_mdev = kzalloc(sizeof(*matrix_mdev), GFP_KERNEL);
-	if (!matrix_mdev) {
-		ret = -ENOMEM;
-		goto err_dec_available;
-	}
+	if (!matrix_mdev)
+		return -ENOMEM;
 	vfio_init_group_dev(&matrix_mdev->vdev, &mdev->dev,
 			    &vfio_ap_matrix_dev_ops);
 
@@ -363,8 +358,6 @@ static int vfio_ap_mdev_probe(struct mdev_device *mdev)
 	mutex_unlock(&matrix_dev->lock);
 	vfio_uninit_group_dev(&matrix_mdev->vdev);
 	kfree(matrix_mdev);
-err_dec_available:
-	atomic_inc(&matrix_dev->available_instances);
 	return ret;
 }
 
@@ -380,7 +373,6 @@ static void vfio_ap_mdev_remove(struct mdev_device *mdev)
 	mutex_unlock(&matrix_dev->lock);
 	vfio_uninit_group_dev(&matrix_mdev->vdev);
 	kfree(matrix_mdev);
-	atomic_inc(&matrix_dev->available_instances);
 }
 
 static ssize_t name_show(struct mdev_type *mtype,
@@ -391,20 +383,8 @@ static ssize_t name_show(struct mdev_type *mtype,
 
 static MDEV_TYPE_ATTR_RO(name);
 
-static ssize_t available_instances_show(struct mdev_type *mtype,
-					struct mdev_type_attribute *attr,
-					char *buf)
-{
-	return sprintf(buf, "%d\n",
-		       atomic_read(&matrix_dev->available_instances));
-}
-
-static MDEV_TYPE_ATTR_RO(available_instances);
-
-
 static struct attribute *vfio_ap_mdev_type_attrs[] = {
 	&mdev_type_attr_name.attr,
-	&mdev_type_attr_available_instances.attr,
 	NULL,
 };
 
@@ -1359,6 +1339,11 @@ static ssize_t vfio_ap_mdev_ioctl(struct vfio_device *vdev,
 	return ret;
 }
 
+static unsigned int vfio_ap_mdev_get_available(struct mdev_type *mtype)
+{
+	return MAX_ZDEV_ENTRIES_EXT;
+}
+
 static const struct vfio_device_ops vfio_ap_matrix_dev_ops = {
 	.open_device = vfio_ap_mdev_open_device,
 	.close_device = vfio_ap_mdev_close_device,
@@ -1374,6 +1359,7 @@ static struct mdev_driver vfio_ap_matrix_driver = {
 	},
 	.probe = vfio_ap_mdev_probe,
 	.remove = vfio_ap_mdev_remove,
+	.get_available = vfio_ap_mdev_get_available,
 };
 
 static const struct mdev_parent_ops vfio_ap_matrix_ops = {
@@ -1387,8 +1373,6 @@ int vfio_ap_mdev_register(void)
 {
 	int ret;
 
-	atomic_set(&matrix_dev->available_instances, MAX_ZDEV_ENTRIES_EXT);
-
 	ret = mdev_register_driver(&vfio_ap_matrix_driver);
 	if (ret)
 		return ret;
diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
index 77760e2b546fe6..dd87c84605bcb6 100644
--- a/drivers/s390/crypto/vfio_ap_private.h
+++ b/drivers/s390/crypto/vfio_ap_private.h
@@ -28,7 +28,6 @@
 /**
  * ap_matrix_dev - the AP matrix device structure
  * @device:	generic device structure associated with the AP matrix device
- * @available_instances: number of mediated matrix devices that can be created
  * @info:	the struct containing the output from the PQAP(QCI) instruction
  * mdev_list:	the list of mediated matrix devices created
  * lock:	mutex for locking the AP matrix device. This lock will be
@@ -39,7 +38,6 @@
  */
 struct ap_matrix_dev {
 	struct device device;
-	atomic_t available_instances;
 	struct ap_config_info info;
 	struct list_head mdev_list;
 	struct mutex lock;
diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c
index c3018e8e6d3258..bb27ca0db948ca 100644
--- a/drivers/vfio/mdev/mdev_core.c
+++ b/drivers/vfio/mdev/mdev_core.c
@@ -25,7 +25,7 @@ static DEFINE_MUTEX(parent_list_lock);
 static struct class_compat *mdev_bus_compat_class;
 
 static LIST_HEAD(mdev_list);
-static DEFINE_MUTEX(mdev_list_lock);
+DEFINE_MUTEX(mdev_list_lock);
 
 struct device *mdev_parent_dev(struct mdev_device *mdev)
 {
@@ -245,6 +245,7 @@ static void mdev_device_release(struct device *dev)
 
 	mutex_lock(&mdev_list_lock);
 	list_del(&mdev->next);
+	mdev->type->available++;
 	mutex_unlock(&mdev_list_lock);
 
 	dev_dbg(&mdev->dev, "MDEV: destroying\n");
@@ -268,6 +269,14 @@ int mdev_device_create(struct mdev_type *type, const guid_t *uuid)
 		}
 	}
 
+	if (drv && drv->get_available) {
+		if (!type->available) {
+			mutex_unlock(&mdev_list_lock);
+			return -EUSERS;
+		}
+		type->available--;
+	}
+
 	mdev = kzalloc(sizeof(*mdev), GFP_KERNEL);
 	if (!mdev) {
 		mutex_unlock(&mdev_list_lock);
diff --git a/drivers/vfio/mdev/mdev_private.h b/drivers/vfio/mdev/mdev_private.h
index afbad7b0a14a17..83586b07023334 100644
--- a/drivers/vfio/mdev/mdev_private.h
+++ b/drivers/vfio/mdev/mdev_private.h
@@ -29,6 +29,7 @@ struct mdev_type {
 	struct kobject *devices_kobj;
 	struct mdev_parent *parent;
 	struct list_head next;
+	unsigned int available;
 	unsigned int type_group_id;
 };
 
@@ -38,6 +39,7 @@ struct mdev_type {
 	container_of(_kobj, struct mdev_type, kobj)
 
 extern struct mdev_driver vfio_mdev_driver;
+extern struct mutex mdev_list_lock;
 
 int  parent_create_sysfs_files(struct mdev_parent *parent);
 void parent_remove_sysfs_files(struct mdev_parent *parent);
diff --git a/drivers/vfio/mdev/mdev_sysfs.c b/drivers/vfio/mdev/mdev_sysfs.c
index d4b99440d19e9a..b3129dfc27ef7d 100644
--- a/drivers/vfio/mdev/mdev_sysfs.c
+++ b/drivers/vfio/mdev/mdev_sysfs.c
@@ -93,8 +93,41 @@ static struct attribute_group mdev_type_std_group = {
 	.attrs = mdev_types_std_attrs,
 };
 
+/* mdev_type attribute used by drivers that have an get_available() op */
+static ssize_t available_instances_show(struct mdev_type *mtype,
+					struct mdev_type_attribute *attr,
+					char *buf)
+{
+	unsigned int available;
+
+	mutex_lock(&mdev_list_lock);
+	available = mtype->available;
+	mutex_unlock(&mdev_list_lock);
+
+	return sysfs_emit(buf, "%u\n", available);
+}
+static MDEV_TYPE_ATTR_RO(available_instances);
+static umode_t available_instances_is_visible(struct kobject *kobj,
+					      struct attribute *attr, int n)
+{
+	struct mdev_type *type = to_mdev_type(kobj);
+
+	if (!type->parent->ops->device_driver->get_available)
+		return 0;
+	return attr->mode;
+}
+static struct attribute *mdev_types_name_attrs[] = {
+	&mdev_type_attr_available_instances.attr,
+	NULL,
+};
+static struct attribute_group mdev_type_available_instances_group = {
+	.attrs = mdev_types_name_attrs,
+	.is_visible = available_instances_is_visible,
+};
+
 static const struct attribute_group *mdev_type_groups[] = {
 	&mdev_type_std_group,
+	&mdev_type_available_instances_group,
 	NULL,
 };
 
@@ -136,6 +169,10 @@ static struct mdev_type *add_mdev_supported_type(struct mdev_parent *parent,
 	mdev_get_parent(parent);
 	type->type_group_id = type_group_id;
 
+	if (parent->ops->device_driver->get_available)
+		type->available =
+			parent->ops->device_driver->get_available(type);
+
 	ret = kobject_init_and_add(&type->kobj, &mdev_type_ktype, NULL,
 				   "%s-%s", dev_driver_string(parent->dev),
 				   group->name);
diff --git a/include/linux/mdev.h b/include/linux/mdev.h
index 8a5fc5d54f9b76..7cadbbac7de9d0 100644
--- a/include/linux/mdev.h
+++ b/include/linux/mdev.h
@@ -120,12 +120,14 @@ struct mdev_type_attribute {
  * @probe: called when new device created
  * @remove: called when device removed
  * @driver: device driver structure
+ * @get_available: Return the max number of instances that can be created
  *
  **/
 struct mdev_driver {
 	int (*probe)(struct mdev_device *dev);
 	void (*remove)(struct mdev_device *dev);
 	struct device_driver driver;
+	unsigned int (*get_available)(struct mdev_type *mtype);
 };
 
 static inline void *mdev_get_drvdata(struct mdev_device *mdev)
diff --git a/samples/vfio-mdev/mdpy.c b/samples/vfio-mdev/mdpy.c
index 402a7ebe656371..d7da6ed3565705 100644
--- a/samples/vfio-mdev/mdpy.c
+++ b/samples/vfio-mdev/mdpy.c
@@ -84,7 +84,6 @@ static dev_t		mdpy_devt;
 static struct class	*mdpy_class;
 static struct cdev	mdpy_cdev;
 static struct device	mdpy_dev;
-static u32		mdpy_count;
 static const struct vfio_device_ops mdpy_dev_ops;
 
 /* State of each mdev device */
@@ -225,9 +224,6 @@ static int mdpy_probe(struct mdev_device *mdev)
 	u32 fbsize;
 	int ret;
 
-	if (mdpy_count >= max_devices)
-		return -ENOMEM;
-
 	mdev_state = kzalloc(sizeof(struct mdev_state), GFP_KERNEL);
 	if (mdev_state == NULL)
 		return -ENOMEM;
@@ -256,8 +252,6 @@ static int mdpy_probe(struct mdev_device *mdev)
 	mdpy_create_config_space(mdev_state);
 	mdpy_reset(mdev_state);
 
-	mdpy_count++;
-
 	ret = vfio_register_emulated_iommu_dev(&mdev_state->vdev);
 	if (ret)
 		goto err_mem;
@@ -284,8 +278,6 @@ static void mdpy_remove(struct mdev_device *mdev)
 	kfree(mdev_state->vconfig);
 	vfio_uninit_group_dev(&mdev_state->vdev);
 	kfree(mdev_state);
-
-	mdpy_count--;
 }
 
 static ssize_t mdpy_read(struct vfio_device *vdev, char __user *buf,
@@ -662,18 +654,10 @@ static ssize_t description_show(struct mdev_type *mtype,
 }
 static MDEV_TYPE_ATTR_RO(description);
 
-static ssize_t available_instances_show(struct mdev_type *mtype,
-					struct mdev_type_attribute *attr,
-					char *buf)
-{
-	return sprintf(buf, "%d\n", max_devices - mdpy_count);
-}
-static MDEV_TYPE_ATTR_RO(available_instances);
 
 static struct attribute *mdev_types_attrs[] = {
 	&mdev_type_attr_name.attr,
 	&mdev_type_attr_description.attr,
-	&mdev_type_attr_available_instances.attr,
 	NULL,
 };
 
@@ -706,6 +690,11 @@ static const struct vfio_device_ops mdpy_dev_ops = {
 	.mmap = mdpy_mmap,
 };
 
+static unsigned int mdpy_get_available(struct mdev_type *mtype)
+{
+	return max_devices;
+}
+
 static struct mdev_driver mdpy_driver = {
 	.driver = {
 		.name = "mdpy",
@@ -715,6 +704,7 @@ static struct mdev_driver mdpy_driver = {
 	},
 	.probe = mdpy_probe,
 	.remove	= mdpy_remove,
+	.get_available = mdpy_get_available,
 };
 
 static const struct mdev_parent_ops mdev_fops = {
