remove xops

tests/kernels/test_prefix_prefill.py

@@ -4,14 +4,16 @@ import time
 
 import pytest
 import torch
-from xformers import ops as xops
-from xformers.ops.fmha.attn_bias import BlockDiagonalCausalFromBottomRightMask
 
-from vllm.attention.backends.xformers import _make_alibi_bias
 from vllm.attention.ops.prefix_prefill import context_attention_fwd
 from vllm.utils import  is_hip
 from vllm.utils import STR_DTYPE_TO_TORCH_DTYPE, seed_everything
 
+if not is_hip():
+    from xformers import ops as xops
+    from xformers.ops.fmha.attn_bias import BlockDiagonalCausalFromBottomRightMask
+    from vllm.attention.backends.xformers import _make_alibi_bias
+
 NUM_HEADS = [64]
 NUM_QUERIES_PER_KV = [1, 8, 64]
 HEAD_SIZES = [128, 96, 24]