vdpa: Modify get_vq_state() to return error code

Modify get_vq_state() so it returns an error code. In case of hardware
acceleration, the available index may be retrieved from the device, an
operation that can possibly fail.

Reviewed-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Eli Cohen <eli@mellanox.com>
Link: https://lore.kernel.org/r/20200804162048.22587-9-eli@mellanox.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>

drivers/vdpa/ifcvf/ifcvf_main.c

@@ -237,12 +237,13 @@ static u16 ifcvf_vdpa_get_vq_num_max(struct vdpa_device *vdpa_dev)
 	return IFCVF_QUEUE_MAX;
 }
 
-static void ifcvf_vdpa_get_vq_state(struct vdpa_device *vdpa_dev, u16 qid,
-				    struct vdpa_vq_state *state)
+static int ifcvf_vdpa_get_vq_state(struct vdpa_device *vdpa_dev, u16 qid,
+				   struct vdpa_vq_state *state)
 {
 	struct ifcvf_hw *vf = vdpa_to_vf(vdpa_dev);
 
 	state->avail_index = ifcvf_get_vq_state(vf, qid);
+	return 0;
 }
 
 static int ifcvf_vdpa_set_vq_state(struct vdpa_device *vdpa_dev, u16 qid,

drivers/vdpa/vdpa_sim/vdpa_sim.c

@@ -464,14 +464,15 @@ static int vdpasim_set_vq_state(struct vdpa_device *vdpa, u16 idx,
 	return 0;
 }
 
-static void vdpasim_get_vq_state(struct vdpa_device *vdpa, u16 idx,
-				 struct vdpa_vq_state *state)
+static int vdpasim_get_vq_state(struct vdpa_device *vdpa, u16 idx,
+				struct vdpa_vq_state *state)
 {
 	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
 	struct vdpasim_virtqueue *vq = &vdpasim->vqs[idx];
 	struct vringh *vrh = &vq->vring;
 
 	state->avail_index = vrh->last_avail_idx;
+	return 0;
 }
 
 static u32 vdpasim_get_vq_align(struct vdpa_device *vdpa)

drivers/vhost/vdpa.c

@@ -375,7 +375,10 @@ static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd,
 		ops->set_vq_ready(vdpa, idx, s.num);
 		return 0;
 	case VHOST_GET_VRING_BASE:
-		ops->get_vq_state(v->vdpa, idx, &vq_state);
+		r = ops->get_vq_state(v->vdpa, idx, &vq_state);
+		if (r)
+			return r;
+
 		vq->last_avail_idx = vq_state.avail_index;
 		break;
 	case VHOST_GET_BACKEND_FEATURES:

include/linux/vdpa.h

@@ -193,8 +193,8 @@ struct vdpa_config_ops {
 	bool (*get_vq_ready)(struct vdpa_device *vdev, u16 idx);
 	int (*set_vq_state)(struct vdpa_device *vdev, u16 idx,
 			    const struct vdpa_vq_state *state);
-	void (*get_vq_state)(struct vdpa_device *vdev, u16 idx,
-			     struct vdpa_vq_state *state);
+	int (*get_vq_state)(struct vdpa_device *vdev, u16 idx,
+			    struct vdpa_vq_state *state);
 	struct vdpa_notification_area
 	(*get_vq_notification)(struct vdpa_device *vdev, u16 idx);
 	/* vq irq is not expected to be changed once DRIVER_OK is set */