vdpa: disable RAM block discard only for the first device

Although it does not make a big difference, its more correct and
simplifies the cleanup path in subsequent patches.

Move ram_block_discard_disable(false) call to the top of
vhost_vdpa_cleanup because:
* We cannot use vhost_vdpa_first_dev after dev->opaque = NULL
  assignment.
* Improve the stack order in cleanup: since it is the last action taken
  in init, it should be the first at cleanup.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Message-Id: <20230303172445.1089785-10-eperezma@redhat.com>
Tested-by: Lei Yang <leiyang@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 14 insertions, 11 deletions

diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index c9a82ce5e0..49afa59261 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -431,16 +431,6 @@ static int vhost_vdpa_init(struct vhost_dev *dev, void *opaque, Error **errp)
     trace_vhost_vdpa_init(dev, opaque);
     int ret;
 
-    /*
-     * Similar to VFIO, we end up pinning all guest memory and have to
-     * disable discarding of RAM.
-     */
-    ret = ram_block_discard_disable(true);
-    if (ret) {
-        error_report("Cannot set discarding of RAM broken");
-        return ret;
-    }
-
     v = opaque;
     v->dev = dev;
     dev->opaque =  opaque ;
@@ -452,6 +442,16 @@ static int vhost_vdpa_init(struct vhost_dev *dev, void *opaque, Error **errp)
         return 0;
     }
 
+    /*
+     * Similar to VFIO, we end up pinning all guest memory and have to
+     * disable discarding of RAM.
+     */
+    ret = ram_block_discard_disable(true);
+    if (ret) {
+        error_report("Cannot set discarding of RAM broken");
+        return ret;
+    }
+
     vhost_vdpa_add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE |
                                VIRTIO_CONFIG_S_DRIVER);
 
@@ -577,12 +577,15 @@ static int vhost_vdpa_cleanup(struct vhost_dev *dev)
     assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_VDPA);
     v = dev->opaque;
     trace_vhost_vdpa_cleanup(dev, v);
+    if (vhost_vdpa_first_dev(dev)) {
+        ram_block_discard_disable(false);
+    }
+
     vhost_vdpa_host_notifiers_uninit(dev, dev->nvqs);
     memory_listener_unregister(&v->listener);
     vhost_vdpa_svq_cleanup(dev);
 
     dev->opaque = NULL;
-    ram_block_discard_disable(false);
 
     return 0;
 }