[fix] prefill unsupport sliding window attention (#2758)

### What this PR does / why we need it?
fix prefill attention bug，not support sliding window.
npu_fused_infer_attention_score head_dim only equal 128, not support
other number.
### Does this PR introduce _any_ user-facing change?
remove prefill phase npu_fused_infer_attention_score
### How was this patch tested?

- vLLM version: v0.10.1.1
- vLLM main:
e599e2c65e

---------

Signed-off-by: nsdie <yeyifan@huawei.com>

tests/ut/attention/test_attention_v1.py

@@ -341,36 +341,6 @@ class TestAscendAttentionBackendImpl(TestBase):
         mock_flash_attention.assert_called_once()
         assert output.shape == (10, 8 * 64)
 
-    @patch('torch_npu._npu_reshape_and_cache')
-    @patch('torch_npu._npu_flash_attention')
-    def test_forward_prefill_no_cache_swa(self, mock_flash_attention,
-                                          mock_reshape_cache):
-        """Test forward pass in PrefillNoCache state"""
-        query = torch.randn(10, 8 * 64)
-        key = torch.randn(10, 8 * 64)
-        value = torch.randn(10, 8 * 64)
-        kv_cache = torch.empty(2, 5, 128, 8, 64)
-        metadata = self.attn_metadata
-        metadata.attn_state = AscendAttentionState.PrefillNoCache
-        metadata.attn_mask = torch.randn(1, 1, 10, 10)
-        metadata.seq_lens = torch.tensor([10])
-        metadata.num_actual_tokens = 10
-        metadata.slot_mapping = torch.zeros(10, dtype=torch.long)
-        layer = self.layer_no_quant
-        # layer.quant_method.apply.return_value = metadata
-        print(self.layer_no_quant._v_scale_float)
-        output = self.impl_swa.forward(layer,
-                                       query,
-                                       key,
-                                       value,
-                                       kv_cache,
-                                       metadata,
-                                       trace_flag=False)
-
-        mock_reshape_cache.assert_called_once()
-        mock_flash_attention.assert_called_once()
-        assert output.shape == (10, 8 * 64)
-
     @patch('torch_npu._npu_reshape_and_cache')
     @patch('torch_npu._npu_flash_attention_qlens')
     def test_forward_prefill_cache_hit(self, mock_flash_attention_qlens,

vllm_ascend/attention/attention_v1.py

@@ -265,20 +265,6 @@ class AscendAttentionBackendImpl(AttentionImpl):
         self.key_cache = None
         self.value_cache = None
 
-    def _repeat_kv(self, hidden_states: torch.Tensor,
-                   n_rep: int) -> torch.Tensor:
-        """
-        This is the equivalent of torch.repeat_interleave(x, dim=1, repeats=n_rep). The hidden states go from (batch,
-        num_key_value_heads, seqlen, head_dim) to (batch, num_attention_heads, seqlen, head_dim)
-        """
-        num_key_value_heads, slen, head_dim = hidden_states.shape
-        if n_rep == 1:
-            return hidden_states
-        hidden_states = hidden_states[:, None, :, :].expand(
-            num_key_value_heads, n_rep, slen, head_dim)
-        return hidden_states.reshape(num_key_value_heads * n_rep, slen,
-                                     head_dim)
-
     def _forward_prefill_no_cache(
         self,
         query: torch.Tensor,
@@ -304,34 +290,15 @@ class AscendAttentionBackendImpl(AttentionImpl):
             mask = torch_npu.npu_format_cast(mask.contiguous(),
                                              ACL_FORMAT_FRACTAL_NZ)
 
-        if self.sliding_window is not None and \
-            attn_metadata.attn_mask.shape[0] > self.sliding_window:
-
-            key = self._repeat_kv(key, self.num_heads // self.num_kv_heads)
-            value = self._repeat_kv(value, self.num_heads // self.num_kv_heads)
-
-            output, _ = torch_npu.npu_fused_infer_attention_score(
-                query,
-                key,
-                value,
-                num_heads=self.num_heads,
-                num_key_value_heads=self.num_kv_heads,
-                input_layout="TND",
-                pre_tokens=self.sliding_window,
-                scale=self.scale,
-                actual_seq_lengths=attn_metadata.seq_lens,
-                actual_seq_lengths_kv=attn_metadata.seq_lens)
-            output = output.view(num_tokens, self.num_heads, self.head_size)
-        else:
-            torch_npu._npu_flash_attention(query=query,
-                                           key=key,
-                                           value=value,
-                                           mask=mask,
-                                           seq_len=attn_metadata.seq_lens,
-                                           scale_value=self.scale,
-                                           num_heads=self.num_heads,
-                                           num_kv_heads=self.num_kv_heads,
-                                           out=output)
+        torch_npu._npu_flash_attention(query=query,
+                                       key=key,
+                                       value=value,
+                                       mask=mask,
+                                       seq_len=attn_metadata.seq_lens,
+                                       scale_value=self.scale,
+                                       num_heads=self.num_heads,
+                                       num_kv_heads=self.num_kv_heads,
+                                       out=output)
         assert output is not None
         return output[:num_tokens, :, :]