[Bugfix] Lazy-import CuteDSL KDA kernel to fix AMD/ROCm startup crash (#21428)

python/sglang/srt/layers/attention/linear/kda_backend.py

@@ -3,9 +3,6 @@ from typing import Tuple, Union
 import torch
 
 from sglang.srt.layers.attention.hybrid_linear_attn_backend import MambaAttnBackendBase
-from sglang.srt.layers.attention.linear.kernels.kda_cutedsl import (
-    CuteDSLKDAKernel,
-)
 from sglang.srt.layers.attention.linear.kernels.kda_triton import TritonKDAKernel
 from sglang.srt.layers.attention.linear.utils import (
     LinearAttnKernelBackend,
@@ -50,6 +47,10 @@ class KDAKernelDispatcher:
         elif decode_backend.is_cutedsl():
             if not is_cuda():
                 raise ValueError("KDA CuTe DSL backend requires CUDA")
+            from sglang.srt.layers.attention.linear.kernels.kda_cutedsl import (
+                CuteDSLKDAKernel,
+            )
+
             self.decode_kernel = CuteDSLKDAKernel()
         else:
             raise ValueError(