[PATCH v5 5/5] vhost-user: fix lost reconnect

[Li Feng]

When the vhost-user is reconnecting to the backend, and if the vhost-user fails
at the get_features in vhost_dev_init(), then the reconnect will fail
and it will not be retriggered forever.

The reason is:
When the vhost-user fails at get_features, the vhost_dev_cleanup will be called
immediately.

vhost_dev_cleanup calls 'memset(hdev, 0, sizeof(struct vhost_dev))'.

The reconnect path is:
vhost_user_blk_event
   vhost_user_async_close(.. vhost_user_blk_disconnect ..)
     qemu_chr_fe_set_handlers <----- clear the notifier callback
       schedule vhost_user_async_close_bh

The vhost->vdev is null, so the vhost_user_blk_disconnect will not be
called, then the event fd callback will not be reinstalled.

All vhost-user devices have this issue, including vhost-user-blk/scsi.

With this patch, if the vdev->vdev is null, the fd callback will still
be reinstalled.

Fixes: 71e076a07d ("hw/virtio: generalise CHR_EVENT_CLOSED handling")

Signed-off-by: Li Feng <fengli@smartx.com>
---
 hw/block/vhost-user-blk.c      | 2 +-
 hw/scsi/vhost-user-scsi.c      | 3 ++-
 hw/virtio/vhost-user-gpio.c    | 2 +-
 hw/virtio/vhost-user.c         | 9 +++++++--
 include/hw/virtio/vhost-user.h | 3 ++-
 5 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
index 3c69fa47d5..95c758200d 100644
--- a/hw/block/vhost-user-blk.c
+++ b/hw/block/vhost-user-blk.c
@@ -391,7 +391,7 @@ static void vhost_user_blk_event(void *opaque, QEMUChrEvent 
event)
     case CHR_EVENT_CLOSED:
         /* defer close until later to avoid circular close */
         vhost_user_async_close(dev, &s->chardev, &s->dev,
-                               vhost_user_blk_disconnect);
+                               vhost_user_blk_disconnect, 
vhost_user_blk_event);
         break;
     case CHR_EVENT_BREAK:
     case CHR_EVENT_MUX_IN:
diff --git a/hw/scsi/vhost-user-scsi.c b/hw/scsi/vhost-user-scsi.c
index 53a62c3170..0effbb4787 100644
--- a/hw/scsi/vhost-user-scsi.c
+++ b/hw/scsi/vhost-user-scsi.c
@@ -238,7 +238,8 @@ static void vhost_user_scsi_event(void *opaque, 
QEMUChrEvent event)
     case CHR_EVENT_CLOSED:
         /* defer close until later to avoid circular close */
         vhost_user_async_close(dev, &vs->conf.chardev, &vsc->dev,
-                               vhost_user_scsi_disconnect);
+                               vhost_user_scsi_disconnect,
+                               vhost_user_scsi_event);
         break;
     case CHR_EVENT_BREAK:
     case CHR_EVENT_MUX_IN:
diff --git a/hw/virtio/vhost-user-gpio.c b/hw/virtio/vhost-user-gpio.c
index d9979aa5db..04c2cc79f4 100644
--- a/hw/virtio/vhost-user-gpio.c
+++ b/hw/virtio/vhost-user-gpio.c
@@ -283,7 +283,7 @@ static void vu_gpio_event(void *opaque, QEMUChrEvent event)
     case CHR_EVENT_CLOSED:
         /* defer close until later to avoid circular close */
         vhost_user_async_close(dev, &gpio->chardev, &gpio->vhost_dev,
-                               vu_gpio_disconnect);
+                               vu_gpio_disconnect, vu_gpio_event);
         break;
     case CHR_EVENT_BREAK:
     case CHR_EVENT_MUX_IN:
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index 8dcf049d42..12c4a41f30 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -2643,6 +2643,7 @@ typedef struct {
     DeviceState *dev;
     CharBackend *cd;
     struct vhost_dev *vhost;
+    IOEventHandler *event_cb;
 } VhostAsyncCallback;
 
 static void vhost_user_async_close_bh(void *opaque)
@@ -2657,7 +2658,10 @@ static void vhost_user_async_close_bh(void *opaque)
      */
     if (vhost->vdev) {
         data->cb(data->dev);
-    }
+    } else if (data->event_cb) {
+        qemu_chr_fe_set_handlers(data->cd, NULL, NULL, data->event_cb,
+                                 NULL, data->dev, NULL, true);
+   }
 
     g_free(data);
 }
@@ -2669,7 +2673,8 @@ static void vhost_user_async_close_bh(void *opaque)
  */
 void vhost_user_async_close(DeviceState *d,
                             CharBackend *chardev, struct vhost_dev *vhost,
-                            vu_async_close_fn cb)
+                            vu_async_close_fn cb,
+                            IOEventHandler *event_cb)
 {
     if (!runstate_check(RUN_STATE_SHUTDOWN)) {
         /*
diff --git a/include/hw/virtio/vhost-user.h b/include/hw/virtio/vhost-user.h
index 191216a74f..649e9dd54f 100644
--- a/include/hw/virtio/vhost-user.h
+++ b/include/hw/virtio/vhost-user.h
@@ -84,6 +84,7 @@ 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);
+                            vu_async_close_fn cb,
+                            IOEventHandler *event_cb);
 
 #endif
-- 
2.41.0