[Multidevice] Tma bulk copy p2p runtime examples

CMakeLists.txt

@@ -1019,6 +1019,7 @@ if(BUILD_TEST)
     ${NVFUSER_ROOT}/tests/cpp/test_multidevice_host_ir.cpp
     ${NVFUSER_ROOT}/tests/cpp/test_multidevice_host_ir_overlap.cpp
     ${NVFUSER_ROOT}/tests/cpp/test_multidevice_ipc.cpp
+    ${NVFUSER_ROOT}/tests/cpp/test_multidevice_tma.cpp
     ${NVFUSER_ROOT}/tests/cpp/test_multidevice_lower_communication.cpp
     ${NVFUSER_ROOT}/tests/cpp/test_multidevice_lower_communication_cuda.cpp
     ${NVFUSER_ROOT}/tests/cpp/test_multidevice_matmul.cpp
@@ -1029,6 +1030,9 @@ if(BUILD_TEST)
     ${NVFUSER_ROOT}/tests/cpp/test_multidevice_transformer.cpp
   )
   add_test_without_main(test_multidevice "${MULTIDEVICE_TEST_SRCS}" "")
+  target_include_directories(test_multidevice PRIVATE
+    "${CMAKE_BINARY_DIR}/include")
+  add_dependencies(test_multidevice nvfuser_rt_tma_copy)
   list(APPEND TEST_BINARIES test_multidevice)
 
   set(MULTIDEVICE_TUTORIAL_SRCS)
@@ -1264,6 +1268,7 @@ list(APPEND NVFUSER_RUNTIME_FILES
   ${NVFUSER_ROOT}/runtime/memory.cu
   ${NVFUSER_ROOT}/runtime/multicast.cu
   ${NVFUSER_SRCS_DIR}/multidevice/alltoallv.cu
+  ${NVFUSER_SRCS_DIR}/multidevice/tma_copy.cu
   ${NVFUSER_ROOT}/runtime/random_numbers.cu
   ${NVFUSER_ROOT}/runtime/tensor_memory.cu
   ${NVFUSER_ROOT}/runtime/tensor.cu

csrc/multidevice/tma_copy.cu

@@ -0,0 +1,103 @@
+// clang-format off
+/*
+* SPDX-FileCopyrightText: Copyright (c) 2025-present NVIDIA CORPORATION & AFFILIATES.
+* All rights reserved.
+* SPDX-License-Identifier: BSD-3-Clause
+*/
+// clang-format on
+//
+// TMA 1D bulk copy kernel (SM90+ / Hopper).
+//
+// This file implements a TMA-based data copy kernel. The build system
+// stringifies it into nvfuser_resources/tma_copy.h (a const char*),
+// which is compiled at runtime via NVRTC. The file is never compiled
+// statically by nvcc.
+//
+// Currently used by tests (test_multidevice_tma.cpp). In a future PR
+// this kernel will be integrated as a P2P and multicast transport
+// alongside the existing SM-based and copy-engine transports in
+// csrc/multidevice/cuda_p2p.cpp.
+//
+// TMA (cp.async.bulk) is a GMEM<->SMEM transfer engine — there is no
+// GMEM-to-GMEM variant. Shared memory staging is inherent to the
+// hardware, so the kernel performs a two-phase copy:
+//
+//   GMEM(src) --[TMA load]--> SMEM --[TMA store]--> GMEM(dst)
+//
+// A single elected thread (thread 0) drives both phases:
+//   1. mbarrier.init (arrival count = 1)
+//   2. mbarrier.arrive.expect_tx (announce expected bytes)
+//   3. cp.async.bulk.shared::cluster.global  (TMA load, async)
+//   4. mbarrier.try_wait.parity (block until load completes)
+//   5. cp.async.bulk.global.shared::cta      (TMA store)
+//   6. cp.async.bulk.commit_group + wait_group.read 0
+//
+// Dynamic shared memory layout (128-byte aligned):
+//   [0, num_bytes)           : staging buffer
+//   [num_bytes, num_bytes+8) : mbarrier (uint64_t)
+
+extern "C" __global__ void __launch_bounds__(32, 1)
+    tma_copy_1d(
+        void* __restrict__ dst,
+        const void* __restrict__ src,
+        int num_bytes) {
+  extern __shared__ __align__(128) unsigned char smem[];
+
+  unsigned long long* mbar =
+      reinterpret_cast<unsigned long long*>(smem + num_bytes);
+  unsigned int smem_addr =
+      static_cast<unsigned int>(__cvta_generic_to_shared(smem));
+  unsigned int mbar_addr =
+      static_cast<unsigned int>(__cvta_generic_to_shared(mbar));
+
+  if (threadIdx.x == 0) {
+    asm volatile(
+        "mbarrier.init.shared::cta.b64 [%0], %1;"
+        ::"r"(mbar_addr), "r"(1));
+    asm volatile(
+        "fence.mbarrier_init.release.cluster;" :::);
+  }
+  __syncwarp();
+
+  if (threadIdx.x == 0) {
+    // Announce expected transaction bytes on the mbarrier
+    asm volatile(
+        "mbarrier.arrive.expect_tx.shared::cta.b64 _, [%0], %1;"
+        ::"r"(mbar_addr), "r"(num_bytes));
+
+    // TMA Load: GMEM -> SMEM (async, completed via mbarrier)
+    asm volatile(
+        "cp.async.bulk.shared::cluster.global"
+        ".mbarrier::complete_tx::bytes"
+        " [%0], [%1], %2, [%3];\n"
+        ::"r"(smem_addr), "l"(src), "r"(num_bytes), "r"(mbar_addr)
+        : "memory");
+
+    // Block until the mbarrier phase flips (TMA load completed)
+    asm volatile(
+        "{\n"
+        ".reg .pred P1;\n"
+        "TMA_COPY_WAIT_LOAD:\n"
+        "mbarrier.try_wait.parity.shared::cta.b64"
+        " P1, [%0], %1;\n"
+        "@P1 bra TMA_COPY_LOAD_DONE;\n"
+        "bra TMA_COPY_WAIT_LOAD;\n"
+        "TMA_COPY_LOAD_DONE:\n"
+        "}"
+        ::"r"(mbar_addr), "r"(0));
+
+    // TMA Store: SMEM -> GMEM
+    asm volatile(
+        "cp.async.bulk.global.shared::cta.bulk_group"
+        " [%0], [%1], %2;\n"
+        ::"l"(dst), "r"(smem_addr), "r"(num_bytes)
+        : "memory");
+    asm volatile("cp.async.bulk.commit_group;");
+    asm volatile(
+        "cp.async.bulk.wait_group.read 0;" ::: "memory");
+
+    asm volatile(
+        "mbarrier.inval.shared::cta.b64 [%0];"
+        ::"r"(mbar_addr));
+  }
+}