!965 doc fix,add GlobalBN only support 2d and 4d

Merge pull request !965 from JichenZhao/globalbn_doc_fix

mindspore/nn/layer/normalization.py

@@ -355,6 +355,9 @@ class GlobalBatchNorm(_BatchNorm):
     .. math::
         y = \frac{x - \mathrm{E}[x]}{\sqrt{\mathrm{Var}[x] + \epsilon}} * \gamma + \beta
 
+    Note:
+        Currently, GlobalBatchNorm only supports 2D and 4D inputs.
+
     Args:
         num_features (int): `C` from an expected input of size (N, C, H, W).
         device_num_each_group (int): The number of devices in each group.

mindspore/ops/operations/comm_ops.py

@@ -156,6 +156,7 @@ class AllGather(PrimitiveWithInfer):
         self.add_prim_attr('group', _get_group(group))
 
     def infer_shape(self, x_shape):
+        validator.check_integer("x shape", len(x_shape), 0, Rel.GT, self.name)
         x_shape[0] = x_shape[0] * self.rank_size
         return x_shape