vhost-user: add VHOST_USER_CHECK_DEVICE_STATE command

After transferring the back-end’s internal state during migration,
check whether the back-end was able to successfully fully process
the state.

The value returned indicates success or error;
0 is success, any non-zero value is an error.

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

2 files changed, 31 insertions, 8 deletions

diff --git a/vhost_user.c b/vhost_user.c
index 747b7f6..2962709 100644
--- a/vhost_user.c
+++ b/vhost_user.c
@@ -981,6 +981,23 @@ static bool vu_set_vring_enable_exec(struct vu_dev *vdev,
 }
 
 /**
+ * vu_check_device_state_exec() -- Return device state migration result
+ * @vdev:	vhost-user device
+ * @vmsg:	vhost-user message
+ *
+ * Return: True as the reply contains the migration result
+ */
+static bool vu_check_device_state_exec(struct vu_dev *vdev,
+				       struct vhost_user_msg *msg)
+{
+	(void)vdev;
+
+	vmsg_set_reply_u64(msg, vdev->device_state_result);
+
+	return true;
+}
+
+/**
  * vu_init() - Initialize vhost-user device structure
  * @c:		execution context
  * @vdev:	vhost-user device
@@ -1001,6 +1018,7 @@ void vu_init(struct ctx *c)
 	}
 	c->vdev->log_table = NULL;
 	c->vdev->log_call_fd = -1;
+	c->vdev->device_state_result = -1;
 }
 
 
@@ -1049,6 +1067,8 @@ void vu_cleanup(struct vu_dev *vdev)
 	vdev->nregions = 0;
 
 	vu_close_log(vdev);
+
+	vdev->device_state_result = -1;
 }
 
 /**
@@ -1079,6 +1099,7 @@ static bool (*vu_handle[VHOST_USER_MAX])(struct vu_dev *vdev,
 	[VHOST_USER_SET_VRING_CALL]	   = vu_set_vring_call_exec,
 	[VHOST_USER_SET_VRING_ERR]	   = vu_set_vring_err_exec,
 	[VHOST_USER_SET_VRING_ENABLE]	   = vu_set_vring_enable_exec,
+	[VHOST_USER_CHECK_DEVICE_STATE]    = vu_check_device_state_exec,
 };
 
 /**
diff --git a/virtio.h b/virtio.h
index f572341..512ec1b 100644
--- a/virtio.h
+++ b/virtio.h
@@ -98,14 +98,15 @@ struct vu_dev_region {
 
 /**
  * struct vu_dev - vhost-user device information
- * @context:		Execution context
- * @nregions:		Number of shared memory regions
- * @regions:		Guest shared memory regions
- * @features:		Vhost-user features
- * @protocol_features:	Vhost-user protocol features
- * @log_call_fd:	Eventfd to report logging update
- * @log_size:		Size of the logging memory region
- * @log_table:		Base of the logging memory region
+ * @context:			Execution context
+ * @nregions:			Number of shared memory regions
+ * @regions:			Guest shared memory regions
+ * @features:			Vhost-user features
+ * @protocol_features:		Vhost-user protocol features
+ * @log_call_fd:		Eventfd to report logging update
+ * @log_size:			Size of the logging memory region
+ * @log_table:			Base of the logging memory region
+ * @device_state_result:	Device state migration result
  */
 struct vu_dev {
 	struct ctx *context;
@@ -117,6 +118,7 @@ struct vu_dev {
 	int log_call_fd;
 	uint64_t log_size;
 	uint8_t *log_table;
+	int device_state_result;
 };
 
 /**