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, 5 insertions, 36 deletions

diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
index 1177064..aff4d2b 100644
--- a/hw/block/vhost-user-blk.c
+++ b/hw/block/vhost-user-blk.c
@@ -369,17 +369,10 @@ static void vhost_user_blk_disconnect(DeviceState *dev)
     vhost_user_blk_stop(vdev);
 
     vhost_dev_cleanup(&s->dev);
-}
 
-static void vhost_user_blk_chr_closed_bh(void *opaque)
-{
-    DeviceState *dev = opaque;
-    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
-    VHostUserBlk *s = VHOST_USER_BLK(vdev);
-
-    vhost_user_blk_disconnect(dev);
+    /* Re-instate the event handler for new connections */
     qemu_chr_fe_set_handlers(&s->chardev, NULL, NULL, vhost_user_blk_event,
-                             NULL, opaque, NULL, true);
+                             NULL, dev, NULL, true);
 }
 
 static void vhost_user_blk_event(void *opaque, QEMUChrEvent event)
@@ -398,33 +391,9 @@ static void vhost_user_blk_event(void *opaque, QEMUChrEvent event)
         }
         break;
     case CHR_EVENT_CLOSED:
-        if (!runstate_check(RUN_STATE_SHUTDOWN)) {
-            /*
-             * A close event may happen during a read/write, but vhost
-             * code assumes the vhost_dev remains setup, so delay the
-             * stop & clear.
-             */
-            AioContext *ctx = qemu_get_current_aio_context();
-
-            qemu_chr_fe_set_handlers(&s->chardev, NULL, NULL, NULL, NULL,
-                    NULL, NULL, false);
-            aio_bh_schedule_oneshot(ctx, vhost_user_blk_chr_closed_bh, opaque);
-
-            /*
-             * Move vhost device to the stopped state. The vhost-user device
-             * will be clean up and disconnected in BH. This can be useful in
-             * the vhost migration code. If disconnect was caught there is an
-             * option for the general vhost code to get the dev state without
-             * knowing its type (in this case vhost-user).
-             *
-             * FIXME: this is sketchy to be reaching into vhost_dev
-             * now because we are forcing something that implies we
-             * have executed vhost_dev_stop() but that won't happen
-             * until vhost_user_blk_stop() gets called from the bh.
-             * Really this state check should be tracked locally.
-             */
-            s->dev.started = false;
-        }
+        /* defer close until later to avoid circular close */
+        vhost_user_async_close(dev, &s->chardev, &s->dev,
+                               vhost_user_blk_disconnect);
         break;
     case CHR_EVENT_BREAK:
     case CHR_EVENT_MUX_IN: