[Spec Decoding] Support MTP for dsv3.2 (#11652)

Co-authored-by: Paiiiiiiiiiiiiii <zengpai@baidu.com>

python/sglang/srt/speculative/draft_utils.py

@@ -48,6 +48,7 @@ class DraftBackendFactory:
             "flashmla": self._create_flashmla_decode_backend,
             "trtllm_mha": self._create_trtllm_mha_decode_backend,
             "trtllm_mla": self._create_trtllm_mla_decode_backend,
+            "nsa": self._create_nsa_decode_backend,
         }
 
         return self._create_backend(
@@ -70,6 +71,7 @@ class DraftBackendFactory:
             "flashmla": self._create_flashmla_prefill_backend,
             "trtllm_mha": self._create_trtllm_mha_prefill_backend,
             "trtllm_mla": self._create_trtllm_mla_prefill_backend,
+            "nsa": self._create_nsa_prefill_backend,
         }
         backend_name = (
             "decode_attention_backend"
@@ -82,6 +84,20 @@ class DraftBackendFactory:
             "EAGLE is not supported in attention backend {backend_type}",
         )
 
+    def _create_nsa_decode_backend(self):
+        from sglang.srt.layers.attention.nsa_backend import (
+            NativeSparseAttnMultiStepBackend,
+        )
+
+        return NativeSparseAttnMultiStepBackend(
+            self.draft_model_runner, self.topk, self.speculative_num_steps
+        )
+
+    def _create_nsa_prefill_backend(self):
+        from sglang.srt.layers.attention.nsa_backend import NativeSparseAttnBackend
+
+        return NativeSparseAttnBackend(self.draft_model_runner, skip_prefill=False)
+
     def _create_flashinfer_decode_backend(self):
         if not get_global_server_args().use_mla_backend:
             from sglang.srt.layers.attention.flashinfer_backend import (