[V0 Deprecation] Deprecate virtual engine

tests/compile/passes/test_rope_kvcache_fusion.py

@@ -295,7 +295,7 @@ def test_rope_kvcache_fusion(
             }
             q_unfused, k_unfused, v_unfused, dummy = model(qkv_unfused, pos_unfused)
             attn_layer = forward_context.no_compile_layers[model.layer_name]
-            kv_cache_unfused = attn_layer.kv_cache[forward_context.virtual_engine]
+            kv_cache_unfused = attn_layer.kv_cache[0]
         del dummy
 
         torch._dynamo.mark_dynamic(qkv, 0)
@@ -309,7 +309,7 @@ def test_rope_kvcache_fusion(
             }
             q_fused, k_fused, v_fused, dummy = model_fused(qkv, pos)
             attn_layer = forward_context.no_compile_layers[model.layer_name]
-            kv_cache_fused = attn_layer.kv_cache[forward_context.virtual_engine]
+            kv_cache_fused = attn_layer.kv_cache[0]
         del dummy
 
         assert fusion_pass.matched_count == 1

tests/v1/kv_connector/unit/test_decode_bench_connector.py

@@ -86,7 +86,7 @@ def __init__(self, block_size: int, num_gpu_blocks: int):
         self._block_hasher = get_request_block_hasher(block_size, sha256)
 
         self._dummy_ctx: ForwardContext = ForwardContext(
-            no_compile_layers={}, attn_metadata={}, virtual_engine=0, slot_mapping={}
+            no_compile_layers={}, attn_metadata={}, slot_mapping={}
         )
 
     def new_request(self, token_ids: list[int]) -> Request:

tests/v1/kv_connector/unit/test_lmcache_integration.py

@@ -211,7 +211,6 @@ def test_forward_context_interface():
     from vllm.forward_context import ForwardContext
 
     assumes(ForwardContext, "no_compile_layers", is_instance_of=dict)
-    assumes(ForwardContext, "virtual_engine")
     assumes(ForwardContext, "attn_metadata")
 
 

tests/v1/kv_connector/unit/test_nixl_connector.py

@@ -580,7 +580,6 @@ def test_multi_xfer_one_engine(
             dummy_ctx = ForwardContext(
                 no_compile_layers={},
                 attn_metadata={},
-                virtual_engine=0,
                 slot_mapping={},
             )
             _before_load = time.perf_counter()
@@ -653,7 +652,6 @@ def test_async_load_kv(
             dummy_ctx = ForwardContext(
                 no_compile_layers={},
                 attn_metadata={},
-                virtual_engine=0,
                 slot_mapping={},
             )
             _before_load = time.perf_counter()
@@ -888,7 +886,6 @@ def test_concurrent_load_kv(
             dummy_ctx = ForwardContext(
                 no_compile_layers={},
                 attn_metadata={},
-                virtual_engine=0,
                 slot_mapping={},
             )
             _before_load = time.perf_counter()
@@ -1057,7 +1054,6 @@ def test_kv_connector_stats(default_vllm_config, dist_init):
     dummy_ctx = ForwardContext(
         no_compile_layers={},
         attn_metadata={},
-        virtual_engine=0,
         slot_mapping={},
     )
     connector.start_load_kv(dummy_ctx)
@@ -1857,7 +1853,6 @@ def test_aborted_request_removed_from_worker_in_batch(default_vllm_config, dist_
     dummy_ctx = ForwardContext(
         no_compile_layers={},
         attn_metadata={},
-        virtual_engine=0,
         slot_mapping={},
     )
     connector.start_load_kv(dummy_ctx)
@@ -2026,7 +2021,6 @@ def test_transfer_failure_logging(
     dummy_ctx = ForwardContext(
         no_compile_layers={},
         attn_metadata={},
-        virtual_engine=0,
         slot_mapping={},
     )
 
@@ -2129,7 +2123,6 @@ def test_handshake_failure_returns_finished(default_vllm_config, dist_init):
     dummy_ctx = ForwardContext(
         no_compile_layers={},
         attn_metadata={},
-        virtual_engine=0,
         slot_mapping={},
     )
     connector.start_load_kv(dummy_ctx)
@@ -2182,7 +2175,6 @@ def test_transfer_setup_failure_returns_finished(default_vllm_config, dist_init)
     dummy_ctx = ForwardContext(
         no_compile_layers={},
         attn_metadata={},
-        virtual_engine=0,
         slot_mapping={},
     )
     connector.start_load_kv(dummy_ctx)

tests/v1/kv_connector/unit/test_offloading_connector.py

@@ -257,7 +257,6 @@ def __init__(
         self._dummy_ctx: ForwardContext = ForwardContext(
             no_compile_layers={},
             attn_metadata={},
-            virtual_engine=0,
             slot_mapping={},
         )
 

vllm/distributed/kv_transfer/kv_connector/v1/example_connector.py

@@ -185,7 +185,7 @@ def inject_kv_into_layer(
                 if kv_cache_attr is None:
                     continue
 
-                kv_cache_layer = kv_cache_attr[forward_context.virtual_engine]
+                kv_cache_layer = kv_cache_attr[0]
 
                 filename = self._generate_filename_debug(
                     layer_name, request.token_ids, request.mm_hashes

vllm/distributed/kv_transfer/kv_connector/v1/lmcache_integration/vllm_v1_adapter.py

@@ -778,9 +778,7 @@ def _init_kv_caches_from_forward_context(self, forward_context: "ForwardContext"
                 continue
 
             if layer_name not in self.kv_caches:
-                self.kv_caches[layer_name] = attn_layer.kv_cache[
-                    forward_context.virtual_engine
-                ]
+                self.kv_caches[layer_name] = attn_layer.kv_cache[0]
 
     ####################
     # Worker side APIs

vllm/distributed/kv_transfer/kv_connector/v1/p2p/p2p_nccl_connector.py

@@ -214,7 +214,7 @@ def inject_kv_into_layer(
                 if kv_cache is None:
                     continue
 
-                layer = kv_cache[forward_context.virtual_engine]
+                layer = kv_cache[0]
 
                 kv_cache = self.p2p_nccl_engine.recv_tensor(
                     request.request_id + "#" + layer_name, remote_address

vllm/forward_context.py

@@ -197,8 +197,6 @@ class ForwardContext:
     for each microbatch.
     Set dynamically for each forward pass
     """
-    # TODO: remove after making all virtual_engines share the same kv cache
-    virtual_engine: int  # set dynamically for each forward pass
     # set dynamically for each forward pass
     dp_metadata: DPMetadata | None = None
     # determine the cudagraph style at runtime to be FULL, PIECEWISE, or NONE.
@@ -265,7 +263,6 @@ def is_forward_context_available() -> bool:
 def create_forward_context(
     attn_metadata: Any,
     vllm_config: VllmConfig,
-    virtual_engine: int = 0,
     dp_metadata: DPMetadata | None = None,
     cudagraph_runtime_mode: CUDAGraphMode = CUDAGraphMode.NONE,
     batch_descriptor: BatchDescriptor | None = None,
@@ -282,7 +279,6 @@ def create_forward_context(
     return ForwardContext(
         no_compile_layers=vllm_config.compilation_config.static_forward_context,
         all_moe_layers=all_moe_layers,
-        virtual_engine=virtual_engine,
         attn_metadata=attn_metadata,
         slot_mapping=slot_mapping or {},
         dp_metadata=dp_metadata,
@@ -313,7 +309,6 @@ def override_forward_context(forward_context: ForwardContext | None):
 def set_forward_context(
     attn_metadata: Any,
     vllm_config: VllmConfig,
-    virtual_engine: int = 0,
     num_tokens: int | None = None,
     num_tokens_across_dp: torch.Tensor | None = None,
     cudagraph_runtime_mode: CUDAGraphMode = CUDAGraphMode.NONE,
@@ -362,7 +357,6 @@ def set_forward_context(
     additional_kwargs = current_platform.set_additional_forward_context(
         attn_metadata=attn_metadata,
         vllm_config=vllm_config,
-        virtual_engine=virtual_engine,
         dp_metadata=dp_metadata,
         num_tokens=num_tokens,
         num_tokens_across_dp=num_tokens_across_dp,
@@ -374,7 +368,6 @@ def set_forward_context(
     forward_context = create_forward_context(
         attn_metadata,
         vllm_config,
-        virtual_engine,
         dp_metadata,
         cudagraph_runtime_mode,
         batch_descriptor,

vllm/model_executor/layers/attention/attention.py

@@ -589,7 +589,7 @@ def get_attention_context(
         - attn_metadata: Attention metadata for this specific layer, or None if
             no metadata available
         - attn_layer: The attention layer instance (Attention or MLAAttention)
-        - kv_cache: The KV cache tensor for current virtual engine
+        - kv_cache: The KV cache tensor for current forward pass
         - slot_mapping: The slot mapping for this specific layer
 
         Note: attn_metadata may be None, but attn_layer and kv_cache are always
@@ -600,7 +600,7 @@ def get_attention_context(
     if isinstance(attn_metadata, dict):
         attn_metadata = attn_metadata[layer_name]
     attn_layer: Attention | MLAAttention = forward_context.no_compile_layers[layer_name]
-    kv_cache = attn_layer.kv_cache[forward_context.virtual_engine]
+    kv_cache = attn_layer.kv_cache[0]
     slot_mapping = forward_context.slot_mapping
     assert isinstance(slot_mapping, dict), (
         f"Expected slot_mapping to be a dict, got {type(slot_mapping)}. "

vllm/model_executor/layers/attention/mla_attention.py

@@ -480,7 +480,7 @@ def forward(
             attn_metadata = forward_context.attn_metadata
             if isinstance(attn_metadata, dict):
                 attn_metadata = attn_metadata[self.layer_name]
-            self_kv_cache = self.kv_cache[forward_context.virtual_engine]
+            self_kv_cache = self.kv_cache[0]
             slot_mapping = forward_context.slot_mapping
 
             assert isinstance(slot_mapping, dict), (
@@ -940,7 +940,7 @@ def unified_mla_kv_cache_update(
         return torch.empty(0, device=kv_c_normed.device, dtype=kv_c_normed.dtype)
 
     attn_layer = forward_context.no_compile_layers[layer_name]
-    kv_cache = attn_layer.kv_cache[forward_context.virtual_engine]
+    kv_cache = attn_layer.kv_cache[0]
 
     slot_mapping = forward_context.slot_mapping
     assert isinstance(slot_mapping, dict), (

vllm/model_executor/layers/attention/static_sink_attention.py

@@ -168,8 +168,7 @@ def forward_native(
             "sink_key and sink_value have not been prepared"
         )
         if not self.sink_populated:
-            forward_context: ForwardContext = get_forward_context()
-            self_kv_cache = self.kv_cache[forward_context.virtual_engine]
+            self_kv_cache = self.kv_cache[0]
             torch.ops.vllm.maybe_populate_sink(self_kv_cache, self.layer_name)
 
         return super().forward(query, key, value, output_shape)

vllm/model_executor/layers/kda.py

@@ -306,7 +306,7 @@ def _forward(
         non_spec_query_start_loc = attn_metadata.non_spec_query_start_loc
         non_spec_state_indices_tensor = attn_metadata.non_spec_state_indices_tensor  # noqa: E501
         num_actual_tokens = attn_metadata.num_actual_tokens
-        constant_caches = self.kv_cache[forward_context.virtual_engine]
+        constant_caches = self.kv_cache[0]
 
         q_proj_states = q_proj_states[:num_actual_tokens]
         k_proj_states = k_proj_states[:num_actual_tokens]

vllm/model_executor/layers/mamba/linear_attn.py

@@ -413,7 +413,7 @@ def _forward(
         qkvact = qkvact.view((qkv.shape[0], self.tp_heads, -1))
         q, k, v = torch.split(qkvact, [self.head_dim] * 3, dim=-1)
         if attn_metadata is not None:
-            kv_cache = self.kv_cache[forward_context.virtual_engine][0]
+            kv_cache = self.kv_cache[0][0]
             state_indices_tensor = attn_metadata.state_indices_tensor
             clear_linear_attention_cache_for_new_sequences(
                 kv_cache, state_indices_tensor, attn_metadata

vllm/model_executor/layers/mamba/mamba_mixer.py

@@ -267,7 +267,7 @@ def forward_impl(self, hidden_states: torch.Tensor, output: torch.Tensor):
             query_start_loc_p = attn_metadata.query_start_loc_p
             state_indices_tensor_p = attn_metadata.state_indices_tensor_p
             state_indices_tensor_d = attn_metadata.state_indices_tensor_d
-            self_kv_cache = self.kv_cache[forward_context.virtual_engine]
+            self_kv_cache = self.kv_cache[0]
             conv_state = self_kv_cache[0].transpose(-1, -2)
             ssm_state = self_kv_cache[1]
             has_initial_states_p = attn_metadata.has_initial_states_p

vllm/model_executor/layers/mamba/mamba_mixer2.py

@@ -575,7 +575,7 @@ def conv_ssm_forward(
             assert isinstance(attn_metadata, dict)
             attn_metadata = attn_metadata[self.prefix]
             assert isinstance(attn_metadata, Mamba2AttentionMetadata)
-            self_kv_cache = self.kv_cache[forward_context.virtual_engine]
+            self_kv_cache = self.kv_cache[0]
             # conv_state = (..., dim, width-1) yet contiguous along 'dim'
             conv_state = self_kv_cache[0].transpose(-1, -2)
             ssm_state = self_kv_cache[1]

vllm/model_executor/layers/mamba/short_conv.py

@@ -117,7 +117,7 @@ def forward_cuda(
             assert isinstance(attn_metadata, dict)
             attn_metadata = attn_metadata[self.prefix]
             assert isinstance(attn_metadata, ShortConvAttentionMetadata)
-            self_kv_cache = self.kv_cache[forward_context.virtual_engine]
+            self_kv_cache = self.kv_cache[0]
             conv_state = self_kv_cache[0].transpose(-1, -2)
             state_indices_tensor_p = attn_metadata.state_indices_tensor_p
             state_indices_tensor_d = attn_metadata.state_indices_tensor_d

vllm/model_executor/models/bailing_moe_linear.py

@@ -709,7 +709,7 @@ def _forward(
 
         # Get KV cache and state indices
         if attn_metadata is not None:
-            kv_cache = self.kv_cache[forward_context.virtual_engine][0]
+            kv_cache = self.kv_cache[0][0]
             state_indices_tensor = attn_metadata.state_indices_tensor
             clear_linear_attention_cache_for_new_sequences(
                 kv_cache, state_indices_tensor, attn_metadata

vllm/model_executor/models/extract_hidden_states.py

@@ -51,7 +51,7 @@ def unified_kv_cache_update(
     """
     forward_context = get_forward_context()
     attn_layer = forward_context.no_compile_layers[layer_name]
-    kv_cache = attn_layer.kv_cache[forward_context.virtual_engine]
+    kv_cache = attn_layer.kv_cache[0]
 
     slot_mapping = forward_context.slot_mapping
     assert isinstance(slot_mapping, dict), (

vllm/model_executor/models/olmo_hybrid.py

@@ -428,7 +428,7 @@ def _forward_core(
         non_spec_token_indx = attn_metadata.non_spec_token_indx
         spec_state_indices_tensor = attn_metadata.spec_state_indices_tensor
         non_spec_state_indices_tensor = attn_metadata.non_spec_state_indices_tensor
-        self_kv_cache = self.kv_cache[forward_context.virtual_engine]
+        self_kv_cache = self.kv_cache[0]
         conv_state = self_kv_cache[0].transpose(-1, -2)
         ssm_state = self_kv_cache[1]
         num_actual_tokens = attn_metadata.num_actual_tokens

vllm/model_executor/models/plamo2.py

@@ -262,7 +262,7 @@ def forward_impl(
             assert isinstance(attn_metadata, dict)
             attn_metadata = attn_metadata[self.prefix]
             assert isinstance(attn_metadata, Mamba2AttentionMetadata)
-            self_kv_cache = self.kv_cache[forward_context.virtual_engine]
+            self_kv_cache = self.kv_cache[0]
             # conv_state = (..., dim, width-1) yet contiguous along 'dim'
             conv_state = self_kv_cache[0].transpose(-1, -2)
             ssm_state = self_kv_cache[1]

vllm/model_executor/models/qwen3_next.py

@@ -815,7 +815,6 @@ def _forward_core(
                 a=a,
                 core_attn_out=core_attn_out,
                 attn_metadata=attn_metadata,
-                virtual_engine=forward_context.virtual_engine,
             )
 
         has_initial_state = attn_metadata.has_initial_state
@@ -826,7 +825,7 @@ def _forward_core(
         non_spec_token_indx = attn_metadata.non_spec_token_indx
         spec_state_indices_tensor = attn_metadata.spec_state_indices_tensor  # noqa: E501
         non_spec_state_indices_tensor = attn_metadata.non_spec_state_indices_tensor  # noqa: E501
-        self_kv_cache = self.kv_cache[forward_context.virtual_engine]
+        self_kv_cache = self.kv_cache[0]
         conv_state = self_kv_cache[0].transpose(-1, -2)
         ssm_state = self_kv_cache[1]
         num_actual_tokens = attn_metadata.num_actual_tokens
@@ -1009,13 +1008,12 @@ def _forward_core_decode_non_spec(
         a: torch.Tensor,
         core_attn_out: torch.Tensor,
         attn_metadata: GDNAttentionMetadata,
-        virtual_engine: int,
     ):
         """
         Core attention computation with a packed non-spec decode fast path.
         """
         non_spec_state_indices_tensor = attn_metadata.non_spec_state_indices_tensor  # noqa: E501
-        self_kv_cache = self.kv_cache[virtual_engine]
+        self_kv_cache = self.kv_cache[0]
         conv_state = self_kv_cache[0].transpose(-1, -2)
         ssm_state = self_kv_cache[1]
         num_actual_tokens = attn_metadata.num_actual_tokens

vllm/v1/worker/utils.py

@@ -510,7 +510,7 @@ def bind_kv_cache(
 
     # Bind kv_caches to forward context
     for layer_name, kv_cache in kv_caches.items():
-        # NOTE: Use list because of v0 PP virtual engine.
+        # NOTE: Keep list wrapper for layers that index kv_cache by engine slot.
         forward_context[layer_name].kv_cache = [kv_cache]