[Tianlei Wu (tianleiwu)]

Summary

Make cuDNN an optional runtime dependency for the CUDA Execution Provider and CUDA Plugin EP. The build still uses cuDNN headers, but provider binaries no longer directly depend on cuDNN shared libraries; cuDNN is loaded lazily when enabled and available, while no-cuDNN runs use native CUDA paths where available and report NOT_IMPLEMENTED for kernels that still require cuDNN.

This also adds CI to validate no-cuDNN runtime environments.

Key Changes

Area	Changes
CUDA EP runtime loading	Added a dynamic cuDNN loader and cuDNN symbol trampolines so CUDA provider binaries can avoid a direct cuDNN dependency.
Provider options	Added enable_cudnn; removed cudnn_path from CUDA EP and CUDA Plugin EP provider configuration.
CUDA Plugin EP	Wired optional cuDNN behavior through plugin EP config, kernel adapters, stream handles, and plugin utilities.
Python preload behavior	Updated Python CUDA preload handling so cuDNN remains an optional dependency instead of an unconditional import/runtime requirement.
Tests	Added/updated provider option coverage and CUDA Plugin EP no-cuDNN mode using ORT_TEST_CUDA_PLUGIN_NO_CUDNN=1.
CI	Added Linux and Windows CUDA no-cuDNN workflows that build with cuDNN headers, exclude cuDNN from the runtime path, verify no direct cuDNN dependency, and run targeted tests.
Documentation	Added docs/CUDA_cuDNN_Optional_Design.md and updated CUDA Plugin EP docs for no-cuDNN behavior and validation.

Testing

Validated locally on Linux CUDA 13:

• Rebuilt CUDA EP / CUDA Plugin EP with cuDNN headers available at build time.
• Verified provider binaries have no direct cuDNN dependency:
  • readelf -d ... | grep NEEDED | grep -i cudnn || echo "no cudnn DT_NEEDED"
  • ldd ... | grep -i cudnn || echo "no cudnn in ldd"
• Ran CUDA Plugin EP no-cuDNN validation:
  • bash .env/cuda_130_plugin_no_cudnn.sh --test_plugin
  • Result: Ran 87 tests, OK (skipped=17)

Additional CI coverage is included for Linux and Windows no-cuDNN CUDA validation.

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[Copilot]

Pull request overview

This PR refactors the CUDA Execution Provider (in-tree and plugin EP) to treat cuDNN as an optional runtime dependency by introducing a lazy loader + cuDNN symbol trampolines, and plumbing a new enable_cudnn provider option through core, plugin, Python, docs, and CI so CUDA can run in no-cuDNN environments (with NOT_IMPLEMENTED for cuDNN-only kernels).

Changes:

• Added a cuDNN dynamic loader (CudnnLibrary) and cuDNN stub/trampoline entry points so provider binaries don’t hard-link cuDNN.
• Introduced enable_cudnn provider option and updated stream/handle creation paths to only create cuDNN handles when enabled and available.
• Updated Python preload behavior, tests, docs, and added Linux/Windows “no cuDNN” CI workflows.

Reviewed changes

Copilot reviewed 29 out of 29 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
onnxruntime/test/python/transformers/test_cuda_plugin_ep.py	Adds no-cuDNN test mode and forces plugin sessions to pass enable_cudnn=0; updates model opset handling and skips cuDNN-only operator tests.
onnxruntime/test/python/onnxruntime_test_python.py	Extends provider-option coverage to include enable_cudnn.
onnxruntime/core/providers/cuda/plugin/cuda_stream_plugin.h	Threads enable_cudnn into plugin stream wrapper state.
onnxruntime/core/providers/cuda/plugin/cuda_stream_plugin.cc	Conditionally initializes plugin cuDNN handles based on enable_cudnn and loader availability.
onnxruntime/core/providers/cuda/plugin/cuda_plugin_utils.h	Improves cuDNN error handling for the plugin EP in no-cuDNN scenarios.
onnxruntime/core/providers/cuda/plugin/cuda_kernel_adapter.h	Adds enable_cudnn to plugin runtime config and guards default cuDNN handle creation/usage.
onnxruntime/core/providers/cuda/plugin/cuda_ep.h	Adds enable_cudnn to plugin EP configuration.
onnxruntime/core/providers/cuda/plugin/cuda_ep.cc	Configures loader policy from plugin EP config and passes enable_cudnn through to adapters/streams.
onnxruntime/core/providers/cuda/plugin/cuda_ep_factory.cc	Parses enable_cudnn from provider/session config for the plugin EP.
onnxruntime/core/providers/cuda/cudnn_stub.cc	Defines cuDNN symbol trampolines that forward via the loader (removes hard DT_NEEDED on cuDNN).
onnxruntime/core/providers/cuda/cudnn_loader.h	Declares the cuDNN runtime loader interface and symbol resolver.
onnxruntime/core/providers/cuda/cudnn_loader.cc	Implements platform-specific dlopen/LoadLibrary and symbol resolution; wires cudnn_frontend dynamic-loading handle.
onnxruntime/core/providers/cuda/cudnn_fe_call.cc	Ensures frontend error paths return NOT_IMPLEMENTED with clear messaging when cuDNN is unavailable.
onnxruntime/core/providers/cuda/cuda_stream_handle.cc	Makes cuDNN handle creation/destruction conditional in stream lifecycle.
onnxruntime/core/providers/cuda/cuda_kernel.h	Ensures kernels that request a cuDNN handle fail clearly when cuDNN is unavailable/disabled.
onnxruntime/core/providers/cuda/cuda_execution_provider.h	Updates per-thread context constructor signature to accept the consolidated provider info (incl. enable_cudnn).
onnxruntime/core/providers/cuda/cuda_execution_provider.cc	Makes per-thread cuDNN handle creation optional and configures loader based on provider option.
onnxruntime/core/providers/cuda/cuda_execution_provider_info.h	Adds enable_cudnn to provider-info struct and hash.
onnxruntime/core/providers/cuda/cuda_execution_provider_info.cc	Parses/emits enable_cudnn in provider options.
onnxruntime/core/providers/cuda/cuda_call.cc	Improves cuDNN-call error handling to surface NOT_IMPLEMENTED when cuDNN isn’t available.
onnxruntime/init.py	Makes cuDNN DLL preloading optional/best-effort (don’t treat missing cuDNN as a preload failure).
docs/cuda_plugin_ep/QUICK_START.md	Documents building/testing the plugin EP in no-cuDNN runtime environments.
docs/cuda_plugin_ep/cuda_plugin_ep_design.md	Documents optional cuDNN runtime dependency model and enable_cudnn semantics for the plugin EP.
docs/CUDA_cuDNN_Optional_Design.md	Adds a design doc describing the phased approach and implementation details for optional cuDNN.
cmake/onnxruntime_python.cmake	Relaxes Windows Python metadata generation when cuDNN DLLs aren’t present.
cmake/onnxruntime_providers_cuda.cmake	Removes direct cuDNN link, enables cudnn_frontend dynamic loading, and keeps cuDNN headers available.
cmake/onnxruntime_providers_cuda_plugin.cmake	Removes direct cuDNN link for the plugin EP and enables cudnn_frontend dynamic loading.
.github/workflows/windows_cuda_no_cudnn.yml	Adds Windows CI to validate no direct cuDNN dependency + no-cuDNN plugin runtime tests.
.github/workflows/linux_cuda_no_cudnn.yml	Adds Linux CI build/smoke validation for in-tree CUDA EP without cuDNN runtime dependency.

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[Copilot]

Pull request overview

Copilot reviewed 31 out of 31 changed files in this pull request and generated 4 comments.

[Copilot]

Pull request overview

Copilot reviewed 31 out of 31 changed files in this pull request and generated 2 comments.

Comments suppressed due to low confidence (1)

onnxruntime/core/providers/cuda/plugin/cuda_kernel_adapter.h:539

• Cleanup on cuBLASLt handle creation failure unconditionally calls cudnnDestroy(it->second.cudnn). If the cuDNN handle was never created (e.g., cuDNN not present), this will still call into the cuDNN stub/loader path unnecessarily. Guard the destroy with a nullptr check (and only null out the handle when it was actually destroyed).

      cudnnDestroy(it->second.cudnn);
      it->second.cudnn = nullptr;