[UX][Attention] Add `attention_config` argument to `LLM()` (#30710)

Signed-off-by: Matthew Bonanni <mbonanni@redhat.com>

vllm/entrypoints/llm.py

@@ -18,6 +18,7 @@ from vllm.beam_search import (
     create_sort_beams_key_function,
 )
 from vllm.config import (
+    AttentionConfig,
     CompilationConfig,
     PoolerConfig,
     ProfilerConfig,
@@ -175,6 +176,10 @@ class LLM:
         compilation_config: Either an integer or a dictionary. If it is an
             integer, it is used as the mode of compilation optimization. If it
             is a dictionary, it can specify the full compilation configuration.
+        attention_config: Configuration for attention mechanisms. Can be a
+            dictionary or an AttentionConfig instance. If a dictionary, it will
+            be converted to an AttentionConfig. Allows specifying the attention
+            backend and other attention-related settings.
         **kwargs: Arguments for [`EngineArgs`][vllm.EngineArgs].
 
     Note:
@@ -213,6 +218,7 @@ class LLM:
         | StructuredOutputsConfig
         | None = None,
         profiler_config: dict[str, Any] | ProfilerConfig | None = None,
+        attention_config: dict[str, Any] | AttentionConfig | None = None,
         kv_cache_memory_bytes: int | None = None,
         compilation_config: int | dict[str, Any] | CompilationConfig | None = None,
         logits_processors: list[str | type[LogitsProcessor]] | None = None,
@@ -252,51 +258,28 @@ class LLM:
         if hf_overrides is None:
             hf_overrides = {}
 
-        if compilation_config is not None:
+        def _make_config(value: Any, cls: type[_R]) -> _R:
+            """Convert dict/None/instance to a config instance."""
+            if value is None:
+                return cls()
+            if isinstance(value, dict):
+                return cls(**{k: v for k, v in value.items() if is_init_field(cls, k)})  # type: ignore[arg-type]
+            return value
+
         if isinstance(compilation_config, int):
             compilation_config_instance = CompilationConfig(
                 mode=CompilationMode(compilation_config)
             )
-            elif isinstance(compilation_config, dict):
-                compilation_config_instance = CompilationConfig(
-                    **{
-                        k: v
-                        for k, v in compilation_config.items()
-                        if is_init_field(CompilationConfig, k)
-                    }
-                )
         else:
-                compilation_config_instance = compilation_config
-        else:
-            compilation_config_instance = CompilationConfig()
-
-        if structured_outputs_config is not None:
-            if isinstance(structured_outputs_config, dict):
-                structured_outputs_instance = StructuredOutputsConfig(
-                    **{
-                        k: v
-                        for k, v in structured_outputs_config.items()
-                        if is_init_field(StructuredOutputsConfig, k)
-                    }
+            compilation_config_instance = _make_config(
+                compilation_config, CompilationConfig
             )
-            else:
-                structured_outputs_instance = structured_outputs_config
-        else:
-            structured_outputs_instance = StructuredOutputsConfig()
 
-        if profiler_config is not None:
-            if isinstance(profiler_config, dict):
-                profiler_config_instance = ProfilerConfig(
-                    **{
-                        k: v
-                        for k, v in profiler_config.items()
-                        if is_init_field(ProfilerConfig, k)
-                    }
+        structured_outputs_instance = _make_config(
+            structured_outputs_config, StructuredOutputsConfig
         )
-            else:
-                profiler_config_instance = profiler_config
-        else:
-            profiler_config_instance = ProfilerConfig()
+        profiler_config_instance = _make_config(profiler_config, ProfilerConfig)
+        attention_config_instance = _make_config(attention_config, AttentionConfig)
 
         # warn about single-process data parallel usage.
         _dp_size = int(kwargs.get("data_parallel_size", 1))
@@ -341,6 +324,7 @@ class LLM:
             pooler_config=pooler_config,
             structured_outputs_config=structured_outputs_instance,
             profiler_config=profiler_config_instance,
+            attention_config=attention_config_instance,
             compilation_config=compilation_config_instance,
             logits_processors=logits_processors,
             **kwargs,