[PATCH v3 6/7] vhost: add vhost_dev_set_owner() / vhost_dev_reset_owner() helpers

[Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>]

Wrap the set_owner/reset_owner backend ops in dev-level helpers, matching
other vhost_dev_* wrappers, so device code can take or release ownership
without reaching into vhost_ops directly.  vhost_dev_init() now uses
vhost_dev_set_owner(). Both return -ENOSYS if the backend has no such op.

No functional change.  These are used by the following vhost-vsock patch to
hand a device between owners during CPR.

Signed-off-by: Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>
---
 hw/virtio/vhost.c         | 20 +++++++++++++++++++-
 include/hw/virtio/vhost.h | 13 +++++++++++++
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index f11588cc51a..7ae2abe33cd 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -1689,6 +1689,24 @@ int vhost_dev_init_backend(struct vhost_dev *hdev, void *opaque,
     return 0;
 }
 
+int vhost_dev_set_owner(struct vhost_dev *hdev)
+{
+    assert(hdev->vhost_ops);
+    if (!hdev->vhost_ops->vhost_set_owner) {
+        return -ENOSYS;
+    }
+    return hdev->vhost_ops->vhost_set_owner(hdev);
+}
+
+int vhost_dev_reset_owner(struct vhost_dev *hdev)
+{
+    assert(hdev->vhost_ops);
+    if (!hdev->vhost_ops->vhost_reset_owner) {
+        return -ENOSYS;
+    }
+    return hdev->vhost_ops->vhost_reset_owner(hdev);
+}
+
 int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
                    VhostBackendType backend_type, uint32_t busyloop_timeout,
                    Error **errp)
@@ -1706,7 +1724,7 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
         goto fail;
     }
 
-    r = hdev->vhost_ops->vhost_set_owner(hdev);
+    r = vhost_dev_set_owner(hdev);
     if (r < 0) {
         error_setg_errno(errp, -r, "vhost_set_owner failed");
         goto fail;
diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
index bc81e09663e..a56a2b66bd5 100644
--- a/include/hw/virtio/vhost.h
+++ b/include/hw/virtio/vhost.h
@@ -175,6 +175,19 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
 int vhost_dev_init_backend(struct vhost_dev *hdev, void *opaque,
                            VhostBackendType backend_type, Error **errp);
 
+/**
+ * vhost_dev_set_owner() / vhost_dev_reset_owner() - take / release ownership
+ * @hdev: the common vhost_dev structure
+ *
+ * Take (VHOST_SET_OWNER) or release (VHOST_RESET_OWNER) ownership of a
+ * device that has already been set up.  Used to hand a device over during
+ * CPR.  Returns -ENOSYS if the backend has no such op.
+ *
+ * Return: 0 on success, negative errno on failure.
+ */
+int vhost_dev_set_owner(struct vhost_dev *hdev);
+int vhost_dev_reset_owner(struct vhost_dev *hdev);
+
 /**
  * vhost_dev_cleanup() - tear down and cleanup vhost interface
  * @hdev: the common vhost_dev structure
-- 
2.47.1