[Bug] Fix Batch Invariant MLA test (#28967)

Signed-off-by: yewentao256 <zhyanwentao@126.com>

tests/v1/determinism/test_batch_invariance.py

@@ -9,13 +9,33 @@ import torch
 from utils import _extract_step_logprobs, _random_prompt, skip_unsupported
 
 from vllm import LLM, SamplingParams
+from vllm.platforms import current_platform
+
+BACKENDS: list[str] = [
+    "FLASH_ATTN",
+    "FLASHINFER",
+]
+
+if current_platform.is_cuda() and current_platform.is_device_capability(90):
+    BACKENDS.append("FLASH_ATTN_MLA")
+
+DEFAULT_MODEL = "Qwen/Qwen3-1.7B"
+MLA_MODEL = "deepseek-ai/DeepSeek-V2-Lite-Chat"
+
+
+def resolve_model_name(backend: str) -> str:
+    """Resolve the model name for the given backend, respecting env overrides."""
+    model = os.getenv("VLLM_TEST_MODEL", DEFAULT_MODEL)
+    if backend.endswith("MLA") and model == DEFAULT_MODEL:
+        return MLA_MODEL
+    return model
 
 
 @skip_unsupported
 @pytest.mark.timeout(1000)
 @pytest.mark.parametrize(
     "backend",
-    ["FLASH_ATTN", "FLASHINFER", "FLASH_ATTN_MLA", "FLASHINFER_MLA", "TRITON_MLA"],
+    BACKENDS,
 )
 def test_v1_generation_is_deterministic_across_batch_sizes_with_needle(
     backend, monkeypatch: pytest.MonkeyPatch
@@ -47,7 +67,7 @@ def test_v1_generation_is_deterministic_across_batch_sizes_with_needle(
     monkeypatch.setenv("VLLM_ATTENTION_BACKEND", backend)
     # Allow overrides from environment (useful for CI tuning)
     # "facebook/opt-125m" is too small, doesn't reliably test determinism
-    model = os.getenv("VLLM_TEST_MODEL", "Qwen/Qwen3-1.7B")
+    model = resolve_model_name(backend)
     num_trials = int(os.getenv("VLLM_NEEDLE_TRIALS", "5"))
     max_batch_size = int(os.getenv("VLLM_NEEDLE_BATCH_SIZE", "128"))
     min_random_prompt = int(os.getenv("VLLM_MIN_PROMPT", "1024"))
@@ -150,7 +170,7 @@ def test_v1_generation_is_deterministic_across_batch_sizes_with_needle(
 @skip_unsupported
 @pytest.mark.parametrize(
     "backend",
-    ["FLASH_ATTN", "FLASHINFER", "FLASH_ATTN_MLA", "FLASHINFER_MLA", "TRITON_MLA"],
+    BACKENDS,
 )
 @pytest.mark.forked
 def test_logprobs_bitwise_batch_invariance_bs1_vs_bsN(
@@ -160,7 +180,7 @@ def test_logprobs_bitwise_batch_invariance_bs1_vs_bsN(
 
     seed = int(os.getenv("VLLM_TEST_SEED", "12345"))
     random.seed(seed)
-    model_name = os.getenv("VLLM_TEST_MODEL", "Qwen/Qwen3-1.7B")
+    model_name = resolve_model_name(backend)
     tp_size = int(os.getenv("VLLM_TEST_TP_SIZE", "1"))
 
     # For batch invariance, disable custom all-reduce to ensure deterministic
@@ -369,7 +389,7 @@ def test_logprobs_bitwise_batch_invariance_bs1_vs_bsN(
 @skip_unsupported
 @pytest.mark.parametrize(
     "backend",
-    ["FLASH_ATTN", "FLASHINFER", "FLASH_ATTN_MLA", "FLASHINFER_MLA", "TRITON_MLA"],
+    BACKENDS,
 )
 def test_simple_generation(backend, monkeypatch: pytest.MonkeyPatch):
     """
@@ -377,7 +397,7 @@ def test_simple_generation(backend, monkeypatch: pytest.MonkeyPatch):
     Useful for quick smoke testing and debugging.
     """
     monkeypatch.setenv("VLLM_ATTENTION_BACKEND", backend)
-    model = os.getenv("VLLM_TEST_MODEL", "Qwen/Qwen3-1.7B")
+    model = resolve_model_name(backend)
 
     llm = LLM(
         model=model,
@@ -419,7 +439,7 @@ def test_simple_generation(backend, monkeypatch: pytest.MonkeyPatch):
 @skip_unsupported
 @pytest.mark.parametrize(
     "backend",
-    ["FLASH_ATTN", "FLASHINFER", "FLASH_ATTN_MLA", "FLASHINFER_MLA", "TRITON_MLA"],
+    BACKENDS,
 )
 @pytest.mark.forked
 def test_logprobs_without_batch_invariance_should_fail(
@@ -434,6 +454,9 @@ def test_logprobs_without_batch_invariance_should_fail(
     The test will PASS if we detect differences (proving batch invariance matters).
     The test will FAIL if everything matches (suggesting batch invariance isn't needed).
     """
+    from vllm.model_executor.layers.batch_invariant import vllm_is_batch_invariant
+
+    vllm_is_batch_invariant.cache_clear()
     monkeypatch.setenv("VLLM_ATTENTION_BACKEND", backend)
 
     # CRITICAL: Disable batch invariance for this test
@@ -441,7 +464,7 @@ def test_logprobs_without_batch_invariance_should_fail(
 
     seed = int(os.getenv("VLLM_TEST_SEED", "12345"))
     random.seed(seed)
-    model_name = os.getenv("VLLM_TEST_MODEL", "Qwen/Qwen3-1.7B")
+    model_name = resolve_model_name(backend)
     tp_size = int(os.getenv("VLLM_TEST_TP_SIZE", "1"))
 
     print(f"\n{'=' * 80}")
@@ -659,7 +682,7 @@ def test_decode_logprobs_match_prefill_logprobs(
 
     seed = int(os.getenv("VLLM_TEST_SEED", "12345"))
     random.seed(seed)
-    model_name = os.getenv("VLLM_TEST_MODEL", "Qwen/Qwen3-1.7B")
+    model_name = resolve_model_name(backend)
     tp_size = int(os.getenv("VLLM_TEST_TP_SIZE", "1"))
 
     from vllm.model_executor.layers.batch_invariant import (

vllm/model_executor/layers/batch_invariant.py

@@ -803,11 +803,11 @@ def override_envs_for_invariance():
         "FLASH_ATTN",  # best supported backend
         "FLASHINFER",
         "FLASH_ATTN_MLA",
-        "FLASHINFER_MLA",
         "TRITON_MLA",
         # Not yet supported MLA backends
         # "FLASHMLA",
         # "FLEX_ATTENTION", # IMA issue even if we disable batch invariance
+        # "FLASHINFER_MLA", https://github.com/vllm-project/vllm/pull/28967
     ]
     if curr_attn_backend not in supported_backends:
         warning = (