hw/virtio: generalise CHR_EVENT_CLOSED handling

..and use for both virtio-user-blk and virtio-user-gpio. This avoids
the circular close by deferring shutdown due to disconnection until a
later point. virtio-user-blk already had this mechanism in place so
generalise it as a vhost-user helper function and use for both blk and
gpio devices.

While we are at it we also fix up vhost-user-gpio to re-establish the
event handler after close down so we can reconnect later.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
Message-Id: <20221130112439.2527228-5-alex.bennee@linaro.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/include/hw/virtio/vhost-user.h b/include/hw/virtio/vhost-user.h
index c6e693cd3f..191216a74f 100644
--- a/include/hw/virtio/vhost-user.h
+++ b/include/hw/virtio/vhost-user.h
@@ -68,4 +68,22 @@ bool vhost_user_init(VhostUserState *user, CharBackend *chr, Error **errp);
  */
 void vhost_user_cleanup(VhostUserState *user);
 
+/**
+ * vhost_user_async_close() - cleanup vhost-user post connection drop
+ * @d: DeviceState for the associated device (passed to callback)
+ * @chardev: the CharBackend associated with the connection
+ * @vhost: the common vhost device
+ * @cb: the user callback function to complete the clean-up
+ *
+ * This function is used to handle the shutdown of a vhost-user
+ * connection to a backend. We handle this centrally to make sure we
+ * do all the steps and handle potential races due to VM shutdowns.
+ * Once the connection is disabled we call a backhalf to ensure
+ */
+typedef void (*vu_async_close_fn)(DeviceState *cb);
+
+void vhost_user_async_close(DeviceState *d,
+                            CharBackend *chardev, struct vhost_dev *vhost,
+                            vu_async_close_fn cb);
+
 #endif