[Flashinfer] Support Flashinfer TRTLLM FP8-qkv BF16/FP16-out Attention Kernel (vllm-project#23647)

Signed-off-by: elvischenv <[email protected]>

Author: elvischenv

benchmarks/kernels/benchmark_trtllm_decode_attention.py

@@ -259,6 +259,7 @@ def write_results_to_csv(results, filename=None):
         # (q_quant_dtype, kv_quant_dtype, o_quant_dtype)
         (None, None, None),
         (None, FP8_DTYPE, None),
+        (FP8_DTYPE, FP8_DTYPE, None),
         (FP8_DTYPE, FP8_DTYPE, FP8_DTYPE),
         (FP8_DTYPE, FP8_DTYPE, FP4_DTYPE),
     ]

benchmarks/kernels/benchmark_trtllm_prefill_attention.py

@@ -274,6 +274,7 @@ def write_results_to_csv(results, filename=None):
     quant_dtypes = [
         # (q_quant_dtype, kv_quant_dtype, o_quant_dtype)
         (None, None, None),
+        (FP8_DTYPE, FP8_DTYPE, None),
         (FP8_DTYPE, FP8_DTYPE, FP8_DTYPE),
         (FP8_DTYPE, FP8_DTYPE, FP4_DTYPE),
     ]

tests/kernels/attention/test_flashinfer_trtllm_attention.py

@@ -35,6 +35,7 @@ def to_float8(x, dtype=torch.float8_e4m3fn):
     # (q_quant_dtype, kv_quant_dtype, o_quant_dtype)
     (None, None, None),
     (None, FP8_DTYPE, None),
+    (FP8_DTYPE, FP8_DTYPE, None),
     (FP8_DTYPE, FP8_DTYPE, FP8_DTYPE),
     (FP8_DTYPE, FP8_DTYPE, FP4_DTYPE),
 ]
@@ -44,6 +45,7 @@ def to_float8(x, dtype=torch.float8_e4m3fn):
 HEAD_SIZE = [128]
 KV_LAYOUT = ["HND"]  # currently only HND is supported
 BLOCK_SIZE = [16]
+WINDOW_LEFT = [-1, 127]
 SOFT_CAP = [None, 50.0]
 
 NUM_BLOCKS = 32768  # Large enough to test overflow in index calculation.
@@ -57,6 +59,7 @@ def to_float8(x, dtype=torch.float8_e4m3fn):
 @pytest.mark.parametrize("head_size", HEAD_SIZE)
 @pytest.mark.parametrize("kv_layout", KV_LAYOUT)
 @pytest.mark.parametrize("block_size", BLOCK_SIZE)
+@pytest.mark.parametrize("window_left", WINDOW_LEFT)
 @pytest.mark.parametrize("soft_cap", SOFT_CAP)
 @torch.inference_mode
 def test_flashinfer_trtllm_decode_with_baseline(
@@ -69,6 +72,7 @@ def test_flashinfer_trtllm_decode_with_baseline(
     head_size: int,
     kv_layout: str,
     block_size: int,
+    window_left: int,
     soft_cap: Optional[float],
 ) -> None:
     torch.set_default_device("cuda")
@@ -155,6 +159,7 @@ def test_flashinfer_trtllm_decode_with_baseline(
                  sm_scale=sm_scale,
                  q_data_type=dtype,
                  kv_data_type=dtype,
+                 window_left=window_left,
                  logits_soft_cap=soft_cap)
 
     output = torch.empty(ref_query.shape, dtype=dtype)
@@ -188,6 +193,7 @@ def test_flashinfer_trtllm_decode_with_baseline(
         max_seq_len=max_seq_len,
         bmm1_scale=q_scale * k_scale * sm_scale,
         bmm2_scale=v_scale / o_scale,
+        window_left=window_left,
         o_sf_scale=o_sf_scale,
         out=output_trtllm,
     )
@@ -222,6 +228,7 @@ def test_flashinfer_trtllm_decode_with_baseline(
 @pytest.mark.parametrize("head_size", HEAD_SIZE)
 @pytest.mark.parametrize("kv_layout", KV_LAYOUT)
 @pytest.mark.parametrize("block_size", BLOCK_SIZE)
+@pytest.mark.parametrize("window_left", WINDOW_LEFT)
 @pytest.mark.parametrize("soft_cap", [None])
 @torch.inference_mode
 def test_flashinfer_trtllm_prefill_with_baseline(
@@ -234,6 +241,7 @@ def test_flashinfer_trtllm_prefill_with_baseline(
     head_size: int,
     kv_layout: str,
     block_size: int,
+    window_left: int,
     soft_cap: Optional[float],
 ) -> None:
     torch.set_default_device("cuda")
@@ -334,6 +342,7 @@ def test_flashinfer_trtllm_prefill_with_baseline(
                  sm_scale=sm_scale,
                  q_data_type=dtype,
                  kv_data_type=dtype,
+                 window_left=window_left,
                  logits_soft_cap=soft_cap)
 
     output = torch.empty(ref_query.shape, dtype=dtype)
@@ -371,6 +380,7 @@ def test_flashinfer_trtllm_prefill_with_baseline(
         batch_size=batch_size,
         cum_seq_lens_q=q_indptr,
         cum_seq_lens_kv=kv_indptr,
+        window_left=window_left,
         o_sf_scale=o_sf_scale,
         out=output_trtllm,
     )
@@ -390,6 +400,8 @@ def test_flashinfer_trtllm_prefill_with_baseline(
         rtol, atol = 4e-1, 1e0
     elif q_quant_dtype == FP8_DTYPE and o_quant_dtype == FP8_DTYPE:
         rtol, atol = 5e-2, 7e-2
+    elif q_quant_dtype == FP8_DTYPE and o_quant_dtype == dtype:
+        rtol, atol = 4e-2, 6e-2
     else:
         rtol, atol = 1e-2, 1e-2
 

vllm/compilation/fusion_attn.py

@@ -258,8 +258,10 @@ def __init__(self, config: VllmConfig):
             pattern_fp8 = AttentionFp8StaticQuantPattern(layer)
             pattern_fp8.register_if_supported(self.patterns)
 
-            pattern_nvfp4 = AttentionNvfp4QuantPattern(layer)
-            pattern_nvfp4.register_if_supported(self.patterns)
+            if current_platform.is_cuda() and hasattr(torch.ops._C,
+                                                      "scaled_fp4_quant"):
+                pattern_nvfp4 = AttentionNvfp4QuantPattern(layer)
+                pattern_nvfp4.register_if_supported(self.patterns)
 
         if len(attn_layers) == 0:
             logger.warning(

vllm/v1/attention/backends/flashinfer.py

@@ -194,19 +194,15 @@ def __init__(self, kv_cache_spec: AttentionSpec, layer_names: list[str],
         FlashInferBackend.validate_head_size(self.head_dim)
         self.page_size = self.kv_cache_spec.block_size
 
-        self.enable_fusion = (
-            self.compilation_config.pass_config.enable_attn_fusion)
-        self.q_data_type = self.model_config.dtype
         self.cache_dtype = self.cache_config.cache_dtype
         if self.cache_dtype.startswith("fp8"):
             self.kv_cache_dtype = (
                 FlashInferBackend.get_fp8_dtype_for_flashinfer(
                     self.cache_dtype))
-            # Insert FP8 quant for query if FP8 kv cache and attn fusion enabled
-            if self.enable_fusion:
-                self.q_data_type = self.kv_cache_dtype
         else:
+            assert self.kv_cache_spec.dtype == self.model_config.dtype
             self.kv_cache_dtype = self.kv_cache_spec.dtype
+        self.q_data_type = self.kv_cache_dtype
 
         self._cascade_wrapper = None  # Wrapper for cascade attention
 
@@ -668,8 +664,6 @@ def forward(
 
         # The attn+quant fusion happens when output_scale is provided.
         if output_scale is None:
-            assert attn_metadata.q_data_type != FP8_DTYPE, \
-                "Query can only be FP8 if output fusion happened."
             assert output_block_scale is None, "output_block_scale "\
                 "is not supported when fusion has not happened"
         else:
@@ -697,7 +691,8 @@ def forward(
                 elif output.dtype == FP4_DTYPE:
                     self.o_sf_scale = layer._o_scale_float
 
-            # Insert FP8 quant for query
+        # Insert FP8 quant for query
+        if attn_metadata.q_data_type == FP8_DTYPE:
             num_tokens, num_heads, head_size = query.shape
             query, _ = ops.scaled_fp8_quant(
                 query.reshape(