virtio: add VIRTIO_F_NOTIFICATION_DATA feature support

According to VirtIO spec v1.2, VIRTIO_F_NOTIFICATION_DATA feature
indicates that the driver passes extra data along with the queue
notifications.

In a split queue case, the extra data is 16-bit available index. In a
packed queue case, the extra data is 1-bit wrap counter and 15-bit
available index.

Add support for this feature for MMIO, channel I/O and modern PCI
transports.

Signed-off-by: Viktor Prutyanov <[e-mail]>
Acked-by: Jason Wang <[e-mail]>
Reviewed-by: Xuan Zhuo <[e-mail]>
Message-Id: <[e-mail]>
Signed-off-by: Michael S. Tsirkin <[e-mail]>

drivers/s390/virtio/virtio_ccw.c

···
 	ccw_device_dma_free(vcdev->cdev, thinint_area, sizeof(*thinint_area));
 }
 
-static bool virtio_ccw_kvm_notify(struct virtqueue *vq)
+static inline bool virtio_ccw_do_kvm_notify(struct virtqueue *vq, u32 data)
 {
 	struct virtio_ccw_vq_info *info = vq->priv;
 	struct virtio_ccw_device *vcdev;
···
 	BUILD_BUG_ON(sizeof(struct subchannel_id) != sizeof(unsigned int));
 	info->cookie = kvm_hypercall3(KVM_S390_VIRTIO_CCW_NOTIFY,
 				      *((unsigned int *)&schid),
-				      vq->index, info->cookie);
+				      data, info->cookie);
 	if (info->cookie < 0)
 		return false;
 	return true;
+}
+
+static bool virtio_ccw_kvm_notify(struct virtqueue *vq)
+{
+	return virtio_ccw_do_kvm_notify(vq, vq->index);
+}
+
+static bool virtio_ccw_kvm_notify_with_data(struct virtqueue *vq)
+{
+	return virtio_ccw_do_kvm_notify(vq, vring_notification_data(vq));
 }
 
 static int virtio_ccw_read_vq_conf(struct virtio_ccw_device *vcdev,
···
 					     struct ccw1 *ccw)
 {
 	struct virtio_ccw_device *vcdev = to_vc_device(vdev);
+	bool (*notify)(struct virtqueue *vq);
 	int err;
 	struct virtqueue *vq = NULL;
 	struct virtio_ccw_vq_info *info;
 	u64 queue;
 	unsigned long flags;
 	bool may_reduce;
+
+	if (__virtio_test_bit(vdev, VIRTIO_F_NOTIFICATION_DATA))
+		notify = virtio_ccw_kvm_notify_with_data;
+	else
+		notify = virtio_ccw_kvm_notify;
 
 	/* Allocate queue. */
 	info = kzalloc(sizeof(struct virtio_ccw_vq_info), GFP_KERNEL);
···
 	may_reduce = vcdev->revision > 0;
 	vq = vring_create_virtqueue(i, info->num, KVM_VIRTIO_CCW_RING_ALIGN,
 				    vdev, true, may_reduce, ctx,
-				    virtio_ccw_kvm_notify, callback, name);
+				    notify, callback, name);
 
 	if (!vq) {
 		/* For now, we fail if we can't get the requested size. */

drivers/virtio/virtio_mmio.c

···
 	return true;
 }
 
+static bool vm_notify_with_data(struct virtqueue *vq)
+{
+	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vq->vdev);
+	u32 data = vring_notification_data(vq);
+
+	writel(data, vm_dev->base + VIRTIO_MMIO_QUEUE_NOTIFY);
+
+	return true;
+}
+
 /* Notify all virtqueues on an interrupt. */
 static irqreturn_t vm_interrupt(int irq, void *opaque)
 {
···
 				  const char *name, bool ctx)
 {
 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
+	bool (*notify)(struct virtqueue *vq);
 	struct virtio_mmio_vq_info *info;
 	struct virtqueue *vq;
 	unsigned long flags;
 	unsigned int num;
 	int err;
+
+	if (__virtio_test_bit(vdev, VIRTIO_F_NOTIFICATION_DATA))
+		notify = vm_notify_with_data;
+	else
+		notify = vm_notify;
 
 	if (!name)
 		return NULL;
···
 
 	/* Create the vring */
 	vq = vring_create_virtqueue(index, num, VIRTIO_MMIO_VRING_ALIGN, vdev,
-				 true, true, ctx, vm_notify, callback, name);
+				 true, true, ctx, notify, callback, name);
 	if (!vq) {
 		err = -ENOMEM;
 		goto error_new_virtqueue;

drivers/virtio/virtio_pci_modern.c

···
 	return vp_modern_config_vector(&vp_dev->mdev, vector);
 }
 
+static bool vp_notify_with_data(struct virtqueue *vq)
+{
+	u32 data = vring_notification_data(vq);
+
+	iowrite32(data, (void __iomem *)vq->priv);
+
+	return true;
+}
+
 static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
 				  struct virtio_pci_vq_info *info,
 				  unsigned int index,
···
 {
 
 	struct virtio_pci_modern_device *mdev = &vp_dev->mdev;
+	bool (*notify)(struct virtqueue *vq);
 	struct virtqueue *vq;
 	u16 num;
 	int err;
+
+	if (__virtio_test_bit(&vp_dev->vdev, VIRTIO_F_NOTIFICATION_DATA))
+		notify = vp_notify_with_data;
+	else
+		notify = vp_notify;
 
 	if (index >= vp_modern_get_num_queues(mdev))
 		return ERR_PTR(-EINVAL);
···
 	vq = vring_create_virtqueue(index, num,
 				    SMP_CACHE_BYTES, &vp_dev->vdev,
 				    true, true, ctx,
-				    vp_notify, callback, name);
+				    notify, callback, name);
 	if (!vq)
 		return ERR_PTR(-ENOMEM);
 

drivers/virtio/virtio_ring.c

···
 }
 EXPORT_SYMBOL_GPL(vring_del_virtqueue);
 
+u32 vring_notification_data(struct virtqueue *_vq)
+{
+	struct vring_virtqueue *vq = to_vvq(_vq);
+	u16 next;
+
+	if (vq->packed_ring)
+		next = (vq->packed.next_avail_idx &
+				~(-(1 << VRING_PACKED_EVENT_F_WRAP_CTR))) |
+			vq->packed.avail_wrap_counter <<
+				VRING_PACKED_EVENT_F_WRAP_CTR;
+	else
+		next = vq->split.avail_idx_shadow;
+
+	return next << 16 | _vq->index;
+}
+EXPORT_SYMBOL_GPL(vring_notification_data);
+
 /* Manipulates transport-specific feature bits. */
 void vring_transport_features(struct virtio_device *vdev)
 {
···
 		case VIRTIO_F_RING_PACKED:
 			break;
 		case VIRTIO_F_ORDER_PLATFORM:
+			break;
+		case VIRTIO_F_NOTIFICATION_DATA:
 			break;
 		default:
 			/* We don't understand this bit. */

include/linux/virtio_ring.h

···
 void vring_transport_features(struct virtio_device *vdev);
 
 irqreturn_t vring_interrupt(int irq, void *_vq);
+
+u32 vring_notification_data(struct virtqueue *_vq);
 #endif /* _LINUX_VIRTIO_RING_H */

include/uapi/linux/virtio_config.h

···
 #define VIRTIO_F_SR_IOV			37
 
 /*
+ * This feature indicates that the driver passes extra data (besides
+ * identifying the virtqueue) in its device notifications.
+ */
+#define VIRTIO_F_NOTIFICATION_DATA	38
+
+/*
  * This feature indicates that the driver can reset a queue individually.
  */
 #define VIRTIO_F_RING_RESET		40