virtio-vdpa: add VIRTIO_F_NOTIFICATION_DATA feature support

Add VIRTIO_F_NOTIFICATION_DATA support for vDPA transport.
If this feature is negotiated, the driver passes extra data when kicking
a virtqueue.

A device that offers this feature needs to implement the
kick_vq_with_data callback.

kick_vq_with_data receives the vDPA device and data.
data includes:
16 bits vqn and 16 bits next available index for split virtqueues.
16 bits vqs, 15 least significant bits of next available index
and 1 bit next_wrap for packed virtqueues.

This patch follows a patch [1] by Viktor Prutyanov which adds support
for the MMIO, channel I/O and modern PCI transports.

Signed-off-by: Alvaro Karsz <[e-mail]>
Message-Id: <[e-mail]>
Signed-off-by: Michael S. Tsirkin <[e-mail]>
Acked-by: Jason Wang <[e-mail]>

drivers/virtio/virtio_vdpa.c

···
 	return true;
 }
 
+static bool virtio_vdpa_notify_with_data(struct virtqueue *vq)
+{
+	struct vdpa_device *vdpa = vd_get_vdpa(vq->vdev);
+	const struct vdpa_config_ops *ops = vdpa->config;
+	u32 data = vring_notification_data(vq);
+
+	ops->kick_vq_with_data(vdpa, data);
+
+	return true;
+}
+
 static irqreturn_t virtio_vdpa_config_cb(void *private)
 {
 	struct virtio_vdpa_device *vd_dev = private;
···
 	struct device *dma_dev;
 	const struct vdpa_config_ops *ops = vdpa->config;
 	struct virtio_vdpa_vq_info *info;
+	bool (*notify)(struct virtqueue *vq) = virtio_vdpa_notify;
 	struct vdpa_callback cb;
 	struct virtqueue *vq;
 	u64 desc_addr, driver_addr, device_addr;
···
 
 	if (index >= vdpa->nvqs)
 		return ERR_PTR(-ENOENT);
+
+	/* We cannot accept VIRTIO_F_NOTIFICATION_DATA without kick_vq_with_data */
+	if (__virtio_test_bit(vdev, VIRTIO_F_NOTIFICATION_DATA)) {
+		if (ops->kick_vq_with_data)
+			notify = virtio_vdpa_notify_with_data;
+		else
+			__virtio_clear_bit(vdev, VIRTIO_F_NOTIFICATION_DATA);
+	}
 
 	/* Queue shouldn't already be set up. */
 	if (ops->get_vq_ready(vdpa, index))
···
 		dma_dev = vdpa_get_dma_dev(vdpa);
 	vq = vring_create_virtqueue_dma(index, max_num, align, vdev,
 					true, may_reduce_num, ctx,
-					virtio_vdpa_notify, callback,
-					name, dma_dev);
+					notify, callback, name, dma_dev);
 	if (!vq) {
 		err = -ENOMEM;
 		goto error_new_virtqueue;

include/linux/vdpa.h

···
  * @kick_vq:			Kick the virtqueue
  *				@vdev: vdpa device
  *				@idx: virtqueue index
+ * @kick_vq_with_data:		Kick the virtqueue and supply extra data
+ *				(only if VIRTIO_F_NOTIFICATION_DATA is negotiated)
+ *				@vdev: vdpa device
+ *				@data for split virtqueue:
+ *				16 bits vqn and 16 bits next available index.
+ *				@data for packed virtqueue:
+ *				16 bits vqn, 15 least significant bits of
+ *				next available index and 1 bit next_wrap.
  * @set_vq_cb:			Set the interrupt callback function for
  *				a virtqueue
  *				@vdev: vdpa device
···
 			      u64 device_area);
 	void (*set_vq_num)(struct vdpa_device *vdev, u16 idx, u32 num);
 	void (*kick_vq)(struct vdpa_device *vdev, u16 idx);
+	void (*kick_vq_with_data)(struct vdpa_device *vdev, u32 data);
 	void (*set_vq_cb)(struct vdpa_device *vdev, u16 idx,
 			  struct vdpa_callback *cb);
 	void (*set_vq_ready)(struct vdpa_device *vdev, u16 idx, bool ready);