[Core] Add Sliding Window Support with Flashinfer (#10462)

Signed-off-by: Pavani Majety <pmajety@nvidia.com>

tests/core/block/e2e/test_correctness_sliding_window.py

@@ -3,6 +3,7 @@ from typing import List
 
 import pytest
 
+from tests.kernels.utils import override_backend_env_variable
 from vllm import LLM, SamplingParams
 
 from .conftest import get_text_from_llm_generator
@@ -28,8 +29,9 @@ BLOCK_SIZE = 16
 @pytest.mark.parametrize("test_llm_kwargs", [{}])
 @pytest.mark.parametrize("batch_size", [5])
 @pytest.mark.parametrize("seed", [1])
+@pytest.mark.parametrize("backend", ["FLASH_ATTN", "FLASHINFER", "XFORMERS"])
 def test_sliding_window_retrival(baseline_llm_generator, test_llm_generator,
-                                 batch_size, seed):
+                                 batch_size, seed, backend, monkeypatch):
     """
     The test does a bunch of assignments "x1 = 10\nx2 = 33\n..." and then
     asks for value of one of them (which is outside the sliding window).
@@ -38,6 +40,8 @@ def test_sliding_window_retrival(baseline_llm_generator, test_llm_generator,
 
     Additionally, we compare the results of the v1 and v2 managers.
     """
+    override_backend_env_variable(monkeypatch, backend)
+
     sampling_params = SamplingParams(
         max_tokens=1024,
         ignore_eos=True,
@@ -84,7 +88,9 @@ def test_sliding_window_retrival(baseline_llm_generator, test_llm_generator,
 @pytest.mark.parametrize("test_llm_kwargs", [{"enable_chunked_prefill": True}])
 @pytest.mark.parametrize("batch_size", [5])
 @pytest.mark.parametrize("seed", [1])
-def test_sliding_window_chunked_prefill(test_llm_generator, batch_size, seed):
+@pytest.mark.parametrize("backend", ["FLASH_ATTN", "FLASHINFER", "XFORMERS"])
+def test_sliding_window_chunked_prefill(test_llm_generator, batch_size, seed,
+                                        backend, monkeypatch):
     """
     This is similar to test_sliding_window_retrival, however, it doesn't
     compare against the v1 block manager since v1 doesn't support
@@ -93,6 +99,8 @@ def test_sliding_window_chunked_prefill(test_llm_generator, batch_size, seed):
     The results with and without chunked prefill are not the same due to
     numerical instabilities.
     """
+    override_backend_env_variable(monkeypatch, backend)
+
     sampling_params = SamplingParams(
         max_tokens=10,
         ignore_eos=True,