vhost: introduce vhost_backend_get_vq_index method

Minusing the idx with the base(dev->vq_index) for vhost-kernel, and
then adding it back for vhost-user doesn't seem right. Here introduces
a new method vhost_backend_get_vq_index() for getting the right vq
index for following vhost messages calls.

Suggested-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Reviewed-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Tested-by: Marcel Apfelbaum <marcel@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/hw/virtio/vhost-backend.h b/include/hw/virtio/vhost-backend.h
index e472f29..e1dfc6d 100644
--- a/include/hw/virtio/vhost-backend.h
+++ b/include/hw/virtio/vhost-backend.h
@@ -24,12 +24,14 @@ typedef int (*vhost_call)(struct vhost_dev *dev, unsigned long int request,
              void *arg);
 typedef int (*vhost_backend_init)(struct vhost_dev *dev, void *opaque);
 typedef int (*vhost_backend_cleanup)(struct vhost_dev *dev);
+typedef int (*vhost_backend_get_vq_index)(struct vhost_dev *dev, int idx);
 
 typedef struct VhostOps {
     VhostBackendType backend_type;
     vhost_call vhost_call;
     vhost_backend_init vhost_backend_init;
     vhost_backend_cleanup vhost_backend_cleanup;
+    vhost_backend_get_vq_index vhost_backend_get_vq_index;
 } VhostOps;
 
 extern const VhostOps user_ops;