start supporting sage blackwell.

src/diffusers/models/attention_dispatch.py

@@ -703,9 +703,16 @@ def _maybe_download_kernel_for_backend(backend: AttentionBackendName) -> None:
     try:
         from kernels import get_kernel
 
-        kernel_module = get_kernel(config.repo_id, revision=config.revision, version=config.version)
+        is_blackwell = torch.cuda.is_available() and torch.cuda.get_device_capability()[0] >= 10  # sm_100+
+        version = 2 if is_blackwell and backend == AttentionBackendName.SAGE_HUB else config.version
+        kernel_module = get_kernel(config.repo_id, revision=config.revision, version=version)
         if needs_kernel:
-            config.kernel_fn = _resolve_kernel_attr(kernel_module, config.function_attr)
+            function_attr = (
+                "sageattn3_blackwell"
+                if is_blackwell and backend == AttentionBackendName.SAGE_HUB
+                else config.function_attr
+            )
+            config.kernel_fn = _resolve_kernel_attr(kernel_module, function_attr)
 
         if needs_wrapped_forward:
             config.wrapped_forward_fn = _resolve_kernel_attr(kernel_module, config.wrapped_forward_attr)