virtio: support unlocked queue kick

EXPORT_SYMBOL_GPL(virtqueue_add_buf);

/**

 * virtqueue_kick - update after add_buf

 * virtqueue_kick_prepare - first half of split virtqueue_kick call.

 * @vq: the struct virtqueue

 *

 * After one or more virtqueue_add_buf calls, invoke this to kick

 * the other side.

 * Instead of virtqueue_kick(), you can do:

 *	if (virtqueue_kick_prepare(vq))

 *		virtqueue_notify(vq);

 *

 * Caller must ensure we don't call this with other virtqueue

 * operations at the same time (except where noted).

 * This is sometimes useful because the virtqueue_kick_prepare() needs

 * to be serialized, but the actual virtqueue_notify() call does not.

 */

void virtqueue_kick(struct virtqueue *_vq)

bool virtqueue_kick_prepare(struct virtqueue *_vq)

{

	struct vring_virtqueue *vq = to_vvq(_vq);

	u16 new, old;

	bool needs_kick;

	START_USE(vq);

	/* Descriptors and available array need to be set before we expose the

	 * new available array entries. */

	/* Need to update avail index before checking if we should notify */

	virtio_mb(vq);

	if (vq->event ?

	    vring_need_event(vring_avail_event(&vq->vring), new, old) :

	    !(vq->vring.used->flags & VRING_USED_F_NO_NOTIFY))

	if (vq->event) {

		needs_kick = vring_need_event(vring_avail_event(&vq->vring),

					      new, old);

	} else {

		needs_kick = !(vq->vring.used->flags & VRING_USED_F_NO_NOTIFY);

	}

	END_USE(vq);

	return needs_kick;

}

EXPORT_SYMBOL_GPL(virtqueue_kick_prepare);

/**

 * virtqueue_notify - second half of split virtqueue_kick call.

 * @vq: the struct virtqueue

 *

 * This does not need to be serialized.

 */

void virtqueue_notify(struct virtqueue *_vq)

{

	struct vring_virtqueue *vq = to_vvq(_vq);

	/* Prod other side to tell it about changes. */

		vq->notify(&vq->vq);

	vq->notify(_vq);

}

EXPORT_SYMBOL_GPL(virtqueue_notify);

	END_USE(vq);

/**

 * virtqueue_kick - update after add_buf

 * @vq: the struct virtqueue

 *

 * After one or more virtqueue_add_buf calls, invoke this to kick

 * the other side.

 *

 * Caller must ensure we don't call this with other virtqueue

 * operations at the same time (except where noted).

 */

void virtqueue_kick(struct virtqueue *vq)

{

	if (virtqueue_kick_prepare(vq))

		virtqueue_notify(vq);

}

EXPORT_SYMBOL_GPL(virtqueue_kick);

void virtqueue_kick(struct virtqueue *vq);

bool virtqueue_kick_prepare(struct virtqueue *vq);

void virtqueue_notify(struct virtqueue *vq);

void *virtqueue_get_buf(struct virtqueue *vq, unsigned int *len);

void virtqueue_disable_cb(struct virtqueue *vq);