[diffusion] feat: support SparseVideoGen2 attention backend (#17507)

Co-authored-by: Mick <mickjagger19@icloud.com>

python/sglang/multimodal_gen/runtime/platforms/cuda.py

@@ -224,6 +224,35 @@ class CudaPlatformBase(Platform):
                 raise ImportError(
                     "Video Sparse Attention backend is not installed."
                 ) from e
+        elif selected_backend == AttentionBackendEnum.SPARSE_VIDEO_GEN_2_ATTN:
+            try:
+                from svg.kernels.triton.permute import (  # noqa: F401
+                    apply_inverse_permutation_triton,
+                    permute_tensor_by_labels_triton,
+                )
+                from svg.kmeans_utils import (  # noqa: F401
+                    batch_kmeans_Euclid,
+                    density_calculation,
+                    dynamic_block_sparse_fwd_flashinfer,
+                    identify_dynamic_map,
+                )
+
+                from sglang.multimodal_gen.runtime.layers.attention.backends.sparse_video_gen_2_attn import (  # noqa: F401
+                    SparseVideoGen2AttentionBackend,
+                )
+
+                logger.info("Using Sparse Video Gen 2 (SAP) Attention backend")
+                return "sglang.multimodal_gen.runtime.layers.attention.backends.sparse_video_gen_2_attn.SparseVideoGen2AttentionBackend"
+            except ImportError as e:
+                logger.error(
+                    "Failed to import Sparse Video Gen 2 (SAP) Attention backend: %s",
+                    str(e),
+                )
+                raise ImportError(
+                    "Sparse Video Gen 2 (SAP) Attention backend is not installed. "
+                    "Please install it by following the instructions at "
+                    "https://github.com/svg-project/Sparse-VideoGen"
+                ) from e
         elif selected_backend == AttentionBackendEnum.VMOBA_ATTN:
             try:
                 from kernel.attn.vmoba_attn.vmoba import moba_attn_varlen  # noqa: F401

python/sglang/multimodal_gen/runtime/platforms/interface.py

@@ -31,6 +31,7 @@ class AttentionBackendEnum(enum.Enum):
     SAGE_ATTN = enum.auto()
     SAGE_ATTN_3 = enum.auto()
     VIDEO_SPARSE_ATTN = enum.auto()
+    SPARSE_VIDEO_GEN_2_ATTN = enum.auto()
     VMOBA_ATTN = enum.auto()
     AITER = enum.auto()
     SLA_ATTN = enum.auto()