[Feature Request]: MACA Support for Mooncake EP/PG #1965

Describe your feature request

Summary

Mooncake EP/PG Python extensions are currently CUDA-only. We need MACA support via cu-bridge without modifying existing source files.

Key Finding

MUSA and HIP do NOT have EP/PG support either — zero references to USE_MUSA/USE_HIP in mooncake-ep/ or mooncake-pg/. This adaptation would be breaking new ground.

Blockers

Proposed Design

Principle: Zero modifications to existing .cpp/.cu/.h files.

1. gpu_vendor/maca.h — Add fabric stubs

static const mcMemAllocationHandleType CU_MEM_HANDLE_TYPE_FABRIC = mcMemHandleTypeNone;
static const mcDrvDeviceAttribute_t CU_DEVICE_ATTRIBUTE_HANDLE_TYPE_FABRIC_SUPPORTED =
    static_cast<mcDrvDeviceAttribute_t>(0x7FFFFFFF);
#define CUmemFabricHandle void*

Remove #define cuDeviceGetAttribute mcDeviceGetAttribute (let cu-bridge handle it).

2. PG — Header mapping only, no source changes

PG uses standard CUDA Runtime APIs. After maca.h is fixed, it should compile as-is.

3. EP Kernel — File-level separation (Ascend-style)

Do not add #ifdef USE_MACA to mooncake_ep_kernel.cu.

Create independent directory:

maca-ep/                          # or mooncake-ep-maca/
├── setup.py
└── src/kernel/
    └── mooncake_ep_kernel_maca.cpp   # stub: throw runtime_error

maca-ep/setup.py references unchanged files from ../mooncake-ep/src/ and swaps only the kernel source.

4. Build system selection

BuildEpExt.cmake chooses directory based on USE_MACA:

if(USE_MACA)
  set(EP_SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/maca-ep")
else()
  set(EP_SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/mooncake-ep")
endif()

Open Questions

1. Directory naming: maca-ep/ vs mooncake-ep-maca/?
2. PG setup.py: separate maca-pg/ directory, or inject via env vars?
3. -include cuda_alike.h via compiler flags (zero source changes) vs explicit #include in headers (one-line change, aligns with transfer-engine convention)?
4. engine.so is empty; libtransfer_engine.so + libasio.so need proper CMake install rules.

Acceptance Criteria

• maca.h contains fabric memory stubs
• mooncake-ep/ and mooncake-pg/ source files remain untouched
• MACA EP compiles & loads (kernel throws runtime_error at call time — expected)
• MACA PG compiles & loads (functional)
• Zero #ifdef USE_MACA in any existing source file

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