SM100 Cutlass MLA decode with unrestricted num_heads (< 128) for DeepSeek TP (#20769)

Signed-off-by: Alexander Matveev <amatveev@redhat.com>

CMakeLists.txt

@@ -553,7 +553,8 @@ if(VLLM_GPU_LANG STREQUAL "CUDA")
   cuda_archs_loose_intersection(MLA_ARCHS "10.0a" "${CUDA_ARCHS}")
   if(${CMAKE_CUDA_COMPILER_VERSION} VERSION_GREATER_EQUAL 12.8 AND MLA_ARCHS)
     set(SRCS
-      "csrc/attention/mla/cutlass_mla_kernels.cu")
+      "csrc/attention/mla/cutlass_mla_kernels.cu"
+      "csrc/attention/mla/sm100_cutlass_mla_kernel.cu")
     set_gencode_flags_for_srcs(
       SRCS "${SRCS}"
       CUDA_ARCHS "${MLA_ARCHS}")

csrc/attention/mla/cutlass_sm100_mla/device/sm100_mla.hpp

+/***************************************************************************************************
+ * Copyright (c) 2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ *
+ * 3. Neither the name of the copyright holder nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ *ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ *LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ *CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ *SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ *INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ *CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ *ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ *POSSIBILITY OF SUCH DAMAGE.
+ *
+ **************************************************************************************************/
+/*
+ * Taken from SGLANG PR https://github.com/sgl-project/sglang/pull/6929
+ * by Alcanderian JieXin Liang
+ */
+
+/*!
+ \file
+ \brief An universal device layer for cutlass 3.x-style kernels.
+*/
+
+// clang-format off
+#pragma once
+
+// common
+#include "cutlass/cutlass.h"
+#include "cutlass/device_kernel.h"
+
+#if !defined(__CUDACC_RTC__)
+#include "cutlass/cluster_launch.hpp"
+#include "cutlass/trace.h"
+#endif // !defined(__CUDACC_RTC__)
+
+#include "../kernel/sm100_fmha_mla_tma_warpspecialized.hpp"
+#include "../kernel/sm100_fmha_mla_reduction.hpp"
+
+////////////////////////////////////////////////////////////////////////////////
+
+namespace cutlass::fmha::device {
+
+using namespace cute;
+using namespace cutlass::fmha::kernel;
+
+
+////////////////////////////////////////////////////////////////////////////////
+////////////////////////////// CUTLASS 3.x API /////////////////////////////////
+////////////////////////////////////////////////////////////////////////////////
+
+template<
+    class Kernel_
+>
+class MLA {
+public:
+
+  using Kernel = Kernel_;
+
+  using ReductionKernel = cutlass::fmha::kernel::Sm100FmhaMlaReductionKernel<
+      typename Kernel::ElementOut,
+      typename Kernel::ElementAcc,
+      typename Kernel::ElementAcc,
+      Kernel::TileShapeH::value,
+      Kernel::TileShapeL::value,
+      256 /*Max split*/
+  >;
+
+  /// Argument structure: User API
+  using KernelArguments = typename Kernel::Arguments;
+  using ReductionArguments = typename ReductionKernel::Arguments;
+
+  using Arguments = KernelArguments;
+
+  /// Argument structure: Kernel API
+  using KernelParams = typename Kernel::Params;
+  using ReductionParams = typename ReductionKernel::Params;
+  struct Params {
+    KernelParams fmha_params;
+    ReductionParams reduction_params;
+  };
+
+private:
+
+  /// Kernel API parameters object
+  Params params_;
+
+  bool is_initialized(bool set = false) {
+    static bool initialized = false;
+    if (set) initialized = true;
+    return initialized;
+  }
+
+  static ReductionArguments to_reduction_args(Arguments const& args) {
+    auto [H, K, D, B] = args.problem_shape;
+    return ReductionArguments{
+      nullptr, args.epilogue.ptr_o, nullptr, args.epilogue.ptr_lse,
+      args.mainloop.softmax_scale, B, args.split_kv, K, args.mainloop.ptr_seq,
+      args.ptr_split_kv, Kernel::TileShapeS::value
+    };
+  }
+
+public:
+
+  /// Access the Params structure
+  Params const& params() const {
+    return params_;
+  }
+
+  static void set_split_kv (KernelArguments& args) {
+    // printf("set_split_kv start");
+    if (args.split_kv >= 1) return;
+    auto [H, K, D, B] = args.problem_shape;
+    // std::cout << H << " " << K << " " << D << " " << B << "\n";      
+    int sm_count = args.hw_info.sm_count;
+    // printf("    sm_count = %d\n", sm_count);
+    int max_splits = ceil_div(K, 128);
+    max_splits = min(16, max_splits);
+    // printf("    max_splits = %d\n", max_splits);
+    int sms_per_batch = max(1, sm_count / B);
+    // printf("    sms_per_batch = %d\n", sms_per_batch);
+    int split_heur = min(max_splits, sms_per_batch);
+    int waves = ceil_div(B * split_heur, sm_count);
+    int k_waves = ceil_div(max_splits, split_heur);
+    int split_wave_aware = ceil_div(max_splits, k_waves);
+    args.split_kv = split_wave_aware;
+    // printf("    args.split_kv = %d\n", args.split_kv);
+
+  }
+
+  /// Determines whether the GEMM can execute the given problem.
+  static Status
+  can_implement(Arguments const& args) {
+    if (! Kernel::can_implement(args)) {
+      return Status::kInvalid;
+    }
+    if (! ReductionKernel::can_implement(to_reduction_args(args))) {
+      return Status::kInvalid;
+    }
+    return Status::kSuccess;
+  }
+
+  /// Gets the workspace size
+  static size_t
+  get_workspace_size(Arguments const& args) {
+    size_t workspace_bytes = 0;
+    workspace_bytes += Kernel::get_workspace_size(args);
+    workspace_bytes += ReductionKernel::get_workspace_size(to_reduction_args(args));
+    return workspace_bytes;
+  }
+
+  /// Computes the maximum number of active blocks per multiprocessor
+  static int maximum_active_blocks(int /* smem_capacity */ = -1) {
+    CUTLASS_TRACE_HOST("MLA::maximum_active_blocks()");
+    int max_active_blocks = -1;
+    int smem_size = Kernel::SharedStorageSize;
+
+    // first, account for dynamic smem capacity if needed
+    cudaError_t result;
+    if (smem_size >= (48 << 10)) {
+      CUTLASS_TRACE_HOST("  Setting smem size to " << smem_size);
+      result = cudaFuncSetAttribute(
+          device_kernel<Kernel>,
+          cudaFuncAttributeMaxDynamicSharedMemorySize,
+          smem_size);
+      if (cudaSuccess != result) {
+        result = cudaGetLastError(); // to clear the error bit
+        CUTLASS_TRACE_HOST(
+          "  cudaFuncSetAttribute() returned error: "
+          << cudaGetErrorString(result));
+        return -1;
+      }
+    }
+
+    // query occupancy after setting smem size
+    result = cudaOccupancyMaxActiveBlocksPerMultiprocessor(
+        &max_active_blocks,
+        device_kernel<Kernel>,
+        Kernel::MaxThreadsPerBlock,
+        smem_size);
+
+    if (cudaSuccess != result) {
+      result = cudaGetLastError(); // to clear the error bit
+      CUTLASS_TRACE_HOST(
+        "  cudaOccupancyMaxActiveBlocksPerMultiprocessor() returned error: "
+        << cudaGetErrorString(result));
+      return -1;
+    }
+
+    CUTLASS_TRACE_HOST("  max_active_blocks: " << max_active_blocks);
+    return max_active_blocks;
+  }
+
+  /// Initializes GEMM state from arguments.
+  Status
+  initialize(Arguments const& args, void* workspace = nullptr, cudaStream_t stream = nullptr) {
+    CUTLASS_TRACE_HOST("MLA::initialize() - workspace "
+      << workspace << ", stream: " << (stream ? "non-null" : "null"));
+
+    // Initialize the workspace
+    Status status = Kernel::initialize_workspace(args, workspace, stream);
+    if (status != Status::kSuccess) {
+      return status;
+    }
+    status = ReductionKernel::initialize_workspace(to_reduction_args(args), workspace, stream);
+    if (status != Status::kSuccess) {
+      return status;
+    }
+    KernelParams kernel_params = Kernel::to_underlying_arguments(args, workspace);
+
+    ReductionArguments reduction_args = to_reduction_args(args);
+    if (reduction_args.split_kv > 1) {
+      reduction_args.ptr_oaccum   = kernel_params.epilogue.ptr_o_acc;
+      reduction_args.ptr_lseaccum = kernel_params.epilogue.ptr_lse_acc;
+    }
+    ReductionParams reduction_params = ReductionKernel::to_underlying_arguments(reduction_args, workspace);
+    // Initialize the Params structure
+    params_ = Params {kernel_params, reduction_params};
+
+    if (is_initialized()) return Status::kSuccess;
+
+    // account for dynamic smem capacity if needed
+    // no dynamic smem is needed for reduction kernel
+    int smem_size = Kernel::SharedStorageSize;
+    if (smem_size >= (48 << 10)) {
+      CUTLASS_TRACE_HOST("  Setting smem size to " << smem_size);
+      cudaError_t result = cudaFuncSetAttribute(
+          device_kernel<Kernel>,
+          cudaFuncAttributeMaxDynamicSharedMemorySize,
+          smem_size);
+      if (cudaSuccess != result) {
+        result = cudaGetLastError(); // to clear the error bit
+        CUTLASS_TRACE_HOST("  cudaFuncSetAttribute() returned error: " << cudaGetErrorString(result));
+        return Status::kErrorInternal;
+      }
+    }
+
+    is_initialized(true);
+
+    return Status::kSuccess;
+  }
+
+  /// Update API is preserved in 3.0, but does not guarantee a lightweight update of params.
+  Status
+  update(Arguments const& args, void* workspace = nullptr) {
+    CUTLASS_TRACE_HOST("MLA()::update() - workspace: " << workspace);
+
+    size_t workspace_bytes = get_workspace_size(args);
+    if (workspace_bytes > 0 && nullptr == workspace) {
+      return Status::kErrorWorkspaceNull;
+    }
+
+    auto fmha_params = Kernel::to_underlying_arguments(args, workspace);
+
+    ReductionArguments reduction_args = to_reduction_args(args);
+    if (reduction_args.split_kv > 1) {
+      reduction_args.ptr_oaccum   = fmha_params.epilogue.ptr_o_acc;
+      reduction_args.ptr_lseaccum = fmha_params.epilogue.ptr_lse_acc;
+    }
+    ReductionParams reduction_params = ReductionKernel::to_underlying_arguments(reduction_args, workspace);
+    // Initialize the Params structure
+    params_ = Params {fmha_params, reduction_params};
+
+    return Status::kSuccess;
+  }
+
+  /// Primary run() entry point API that is static allowing users to create and manage their own params.
+  /// Supplied params struct must be construct by calling Kernel::to_underling_arguments()
+  static Status
+  run(Params& params, cudaStream_t stream = nullptr) {
+    CUTLASS_TRACE_HOST("MLA::run()");
+    dim3 const block = Kernel::get_block_shape();
+    dim3 const grid = Kernel::get_grid_shape(params.fmha_params);
+
+    // configure smem size and carveout
+    int smem_size = Kernel::SharedStorageSize;
+
+    Status launch_result;
+    // Use extended launch API only for mainloops that use it
+    if constexpr(Kernel::ArchTag::kMinComputeCapability >= 90) {
+      dim3 cluster(cute::size<0>(typename Kernel::ClusterShape{}),
+                   cute::size<1>(typename Kernel::ClusterShape{}),
+                   cute::size<2>(typename Kernel::ClusterShape{}));
+      void const* kernel = (void const*) device_kernel<Kernel>;
+      void* kernel_params[] = {&params.fmha_params};
+      launch_result = ClusterLauncher::launch(grid, cluster, block, smem_size, stream, kernel, kernel_params);
+    }
+    else {
+      launch_result = Status::kSuccess;
+      device_kernel<Kernel><<<grid, block, smem_size, stream>>>(params.fmha_params);
+    }
+
+    cudaError_t result = cudaGetLastError();
+    if (cudaSuccess != result or Status::kSuccess != launch_result) {
+      //return Status::kSuccess;
+      CUTLASS_TRACE_HOST("  Kernel launch failed. Reason: " << result);
+      return Status::kErrorInternal;
+    }
+    if (params.reduction_params.split_kv > 1) {
+      // launch reduction kernel
+      dim3 const block = ReductionKernel::get_block_shape();
+      dim3 const grid  = ReductionKernel::get_grid_shape(params.reduction_params);
+      device_kernel<ReductionKernel><<<grid, block, 0, stream>>>(params.reduction_params);
+      cudaError_t result = cudaGetLastError();
+      if (cudaSuccess == result) {
+        return Status::kSuccess;
+      }
+      else {
+        CUTLASS_TRACE_HOST("  Kernel launch failed. Reason: " << result);
+        return Status::kErrorInternal;
+      }
+    }
+    else {
+      return Status::kSuccess;
+    }
+  }
+
+  //
+  // Non-static launch overloads that first create and set the internal params struct of this kernel handle.
+  //
+
+  /// Launches the kernel after first constructing Params internal state from supplied arguments.
+  Status
+  run(Arguments const& args, void* workspace = nullptr, cudaStream_t stream = nullptr) {
+    Status status = initialize(args, workspace, stream);
+    if (Status::kSuccess == status) {
+      status = run(params_, stream);
+    }
+    return status;
+  }
+
+  /// Launches the kernel after first constructing Params internal state from supplied arguments.
+  Status
+  operator()(Arguments const& args, void* workspace = nullptr, cudaStream_t stream = nullptr) {
+    return run(args, workspace, stream);
+  }
+
+  /// Overload that allows a user to re-launch the same kernel without updating internal params struct.
+  Status
+  run(cudaStream_t stream = nullptr) {
+    return run(params_, stream);
+  }
+
+  /// Overload that allows a user to re-launch the same kernel without updating internal params struct.
+  Status
+  operator()(cudaStream_t stream = nullptr) {
+    return run(params_, stream);
+  }
+};
+
+////////////////////////////////////////////////////////////////////////////////
+
+} // namespace cutlass::fmha::device
+
+////////////////////////////////////////////////////////////////////////////////

csrc/attention/mla/cutlass_sm100_mla/kernel/sm100_fmha_mla_reduction.hpp

+/***************************************************************************************************
+ * Copyright (c) 2024 - 2025 NVIDIA CORPORATION & AFFILIATES. All rights
+ *reserved. SPDX-License-Identifier: BSD-3-Clause
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ *
+ * 3. Neither the name of the copyright holder nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ *ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ *LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ *CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ *SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ *INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ *CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ *ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ *POSSIBILITY OF SUCH DAMAGE.
+ *
+ **************************************************************************************************/
+/*
+ * Taken from SGLANG PR https://github.com/sgl-project/sglang/pull/6929
+ * by Alcanderian JieXin Liang
+ */
+
+// clang-format off
+#pragma once
+
+#include "cutlass/cutlass.h"
+#include "cutlass/arch/arch.h"
+#include "cute/tensor.hpp"
+
+namespace cutlass::fmha::kernel {
+
+using namespace cute;
+template<
+    class ElementOut,
+    class ElementAcc,
+    class ElementScale,
+    size_t kNumHeads,
+    size_t kHeadDimLatent,
+    int kMaxSplits
+>
+struct Sm100FmhaMlaReductionKernel {
+
+  static const int SharedStorageSize = 0;
+  static const int MaxThreadsPerBlock = 128;
+  static const int MinBlocksPerMultiprocessor = 1;
+
+  using ArchTag = cutlass::arch::Sm100;
+
+  static_assert(kHeadDimLatent % MaxThreadsPerBlock == 0);
+  struct Arguments {
+    ElementAcc* ptr_oaccum = nullptr;
+    ElementOut* ptr_o = nullptr;
+    ElementAcc* ptr_lseaccum = nullptr;
+    ElementAcc* ptr_lse = nullptr;
+    ElementScale scale = 1.f;
+    int num_batches = 0;
+    int split_kv = -1;
+    int dim_k = -1;
+    int* ptr_seq = nullptr;
+    int* ptr_split_kv = nullptr;
+    int tile_shape_s = 128;
+  };
+  using Params = Arguments;
+
+  static Params to_underlying_arguments(Arguments const& args, void* workspace) {
+    return {args.ptr_oaccum, args.ptr_o, args.ptr_lseaccum, args.ptr_lse,
+	    args.scale, args.num_batches, args.split_kv, args.dim_k, args.ptr_seq,
+	    args.ptr_split_kv, args.tile_shape_s};
+  }
+
+  static size_t get_workspace_size(Arguments const& /*args*/) {
+    return 0;
+  }
+
+  static Status initialize_workspace(
+      Arguments const& /*args*/, void* /*ws*/, cudaStream_t /*stream*/) {
+    return Status::kSuccess;
+  }
+
+  static dim3 get_grid_shape(Params const& params) {
+    return dim3(kNumHeads, 1, params.num_batches);
+  }
+
+  static dim3 get_block_shape() {
+    return dim3(MaxThreadsPerBlock, 1, 1);
+  }
+
+  static bool can_implement(Arguments const& args) {
+    if (args.num_batches <= 0) return false;
+    if (args.split_kv <= 0) return false;
+    return true;
+  }
+
+  CUTLASS_DEVICE void operator() (Params const& params, char* smem_raw) {
+    if (params.split_kv <= 1) return;
+    auto blk_coord = make_coord(blockIdx.x, _0{}, blockIdx.z);
+
+    __shared__ ElementAcc sLseScale[kMaxSplits];
+    const size_t offset_lseaccum = get<0>(blk_coord) + kNumHeads * params.split_kv * get<2>(blk_coord);
+    const size_t offset_lse = get<0>(blk_coord) + kNumHeads * get<2>(blk_coord);
+
+    Tensor gLSEaccum = make_tensor(make_gmem_ptr(params.ptr_lseaccum + offset_lseaccum),
+                                   make_shape(params.split_kv), Stride<Int<kNumHeads>>{});
+
+    Tensor gLSE = make_tensor(make_gmem_ptr(params.ptr_lse + offset_lse),
+                              Shape<_1>{}, Stride<_1>{});
+
+    auto dim_k = params.ptr_seq == nullptr ?  params.dim_k : params.ptr_seq[get<2>(blk_coord)];
+    auto local_split_kv = params.ptr_split_kv == nullptr ? params.split_kv : params.ptr_split_kv[get<2>(blk_coord)];
+    auto k_tile_total = ceil_div(dim_k, params.tile_shape_s);
+    auto k_tile_per_cta = ceil_div(k_tile_total, local_split_kv);
+    local_split_kv = ceil_div(k_tile_total, k_tile_per_cta);
+
+    int warp_idx = cutlass::canonical_warp_idx_sync();
+    if (warp_idx == 0) {
+      constexpr int kNLsePerThread = cute::ceil_div(kMaxSplits, 32);
+
+      ElementAcc local_lse[kNLsePerThread];
+
+      CUTLASS_PRAGMA_UNROLL
+      for (int i = 0; i < kNLsePerThread; ++i) {
+        const int split = i * 32 + threadIdx.x;
+        local_lse[i] = split < local_split_kv ? gLSEaccum(split) : -std::numeric_limits<ElementAcc>::infinity();
+      }
+
+      ElementAcc lse_max = -std::numeric_limits<ElementAcc>::infinity();
+      CUTLASS_PRAGMA_UNROLL
+      for (int i = 0; i < kNLsePerThread; ++i) {
+        lse_max = max(lse_max, local_lse[i]);
+      }
+      CUTLASS_PRAGMA_UNROLL
+      for (int offset = 16; offset >= 1; offset /= 2) {
+        lse_max = max(lse_max, __shfl_xor_sync(0xffffffff, lse_max, offset));
+      }
+      lse_max = lse_max == -std::numeric_limits<ElementAcc>::infinity() ? 0.0f : lse_max;  // In case all local LSEs are -inf
+      lse_max = __shfl_sync(0xffffffff, lse_max, 0);
+
+      ElementAcc sum_lse = 0;
+      CUTLASS_PRAGMA_UNROLL
+      for (int i = 0; i < kNLsePerThread; ++i) {
+        sum_lse = sum_lse + expf(local_lse[i] - lse_max);
+      }
+
+      CUTLASS_PRAGMA_UNROLL
+      for (int offset = 16; offset >= 1; offset /= 2) {
+        sum_lse = sum_lse + __shfl_xor_sync(0xffffffff, sum_lse, offset);
+      }
+
+      sum_lse = __shfl_sync(0xffffffff, sum_lse, 0);
+
+      ElementAcc global_lse = (sum_lse == 0.f || sum_lse != sum_lse) ? std::numeric_limits<ElementAcc>::infinity() : logf(sum_lse) + lse_max;
+      if (threadIdx.x == 0 and params.ptr_lse != nullptr) {
+        gLSE(0) = global_lse;
+      }
+
+      CUTLASS_PRAGMA_UNROLL
+      for (int i = 0; i < kNLsePerThread; ++i) {
+        const int split = i * 32 + threadIdx.x;
+        if (split < local_split_kv) {
+          sLseScale[split] = expf(local_lse[i] - global_lse);
+        }
+      }
+    }
+    __syncthreads();
+
+    constexpr int Elements = kHeadDimLatent / MaxThreadsPerBlock;
+    const size_t offset_oaccum = kHeadDimLatent * params.split_kv * (get<0>(blk_coord) + kNumHeads * get<2>(blk_coord));
+    Tensor gOaccum = make_tensor(make_gmem_ptr(params.ptr_oaccum + offset_oaccum),
+                               Shape<Int<kHeadDimLatent>>{}, Stride<_1>{});
+    ElementAcc local_val[Elements] = {0};
+    for (int split = 0; split < local_split_kv; ++split) {
+      ElementAcc lse_scale = sLseScale[split];
+      CUTLASS_PRAGMA_UNROLL
+      for(int i = 0; i < Elements; ++i) {
+        local_val[i] += lse_scale * gOaccum(threadIdx.x + MaxThreadsPerBlock * i);
+      }
+      gOaccum.data() = gOaccum.data() + kHeadDimLatent;
+    }
+    auto ptr_o_local = params.ptr_o + (get<0>(blk_coord) + get<2>(blk_coord) * kNumHeads) * kHeadDimLatent;
+    Tensor gO = make_tensor(make_gmem_ptr(ptr_o_local), Shape<Int<kHeadDimLatent>>{}, Stride<_1>{});
+
+    CUTLASS_PRAGMA_UNROLL
+    for(int i = 0; i < Elements; ++i) {
+      gO(threadIdx.x + MaxThreadsPerBlock * i) = static_cast<ElementOut>(local_val[i]);
+    }
+  }
+};
+
+}  // namespace cutlass::fmha::kernel

csrc/attention/mla/cutlass_sm100_mla/kernel/sm100_mla_tile_scheduler.hpp

+/***************************************************************************************************
+ * Copyright (c) 2024 - 2025 NVIDIA CORPORATION & AFFILIATES. All rights
+ *reserved. SPDX-License-Identifier: BSD-3-Clause
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ *
+ * 3. Neither the name of the copyright holder nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ *ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ *LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ *CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ *SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ *INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ *CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ *ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ *POSSIBILITY OF SUCH DAMAGE.
+ *
+ **************************************************************************************************/
+/*
+ * Taken from SGLANG PR https://github.com/sgl-project/sglang/pull/6929
+ * by Alcanderian JieXin Liang
+ */
+
+// clang-format off
+#pragma once
+
+#include "cutlass/cutlass.h"
+#include "cutlass/fast_math.h"
+#include "cutlass/kernel_hardware_info.h"
+
+namespace cutlass::fmha::kernel {
+
+////////////////////////////////////////////////////////////////////////////////
+
+struct Sm100MlaIndividualTileScheduler {
+
+  struct Params {
+    dim3 grid;
+  };
+
+  bool valid_ = true;
+
+  CUTLASS_DEVICE
+  Sm100MlaIndividualTileScheduler(Params const&) {}
+
+  template<class ProblemShape, class ClusterShape>
+  static Params to_underlying_arguments(
+      ProblemShape const& problem_shape, KernelHardwareInfo hw_info,
+      ClusterShape const& cluster_shape, int const& split_kv) {
+    using namespace cute;
+    dim3 grid(get<0>(cluster_shape), get<3>(problem_shape) /* Batch */, split_kv /*Maximum Split KV*/);
+    return Params{ grid };
+  }
+
+  static dim3 get_grid_shape(Params const& params) {
+    return params.grid;
+  }
+
+  CUTLASS_DEVICE
+  bool is_valid() {
+    return valid_;
+  }
+
+  CUTLASS_DEVICE
+  auto get_block_coord() {
+    using namespace cute;
+    return make_coord(blockIdx.x, _0{}, blockIdx.y, blockIdx.z);
+  }
+
+  CUTLASS_DEVICE
+  Sm100MlaIndividualTileScheduler& operator++() {
+    valid_ = false;
+    return *this;
+  }
+};
+
+////////////////////////////////////////////////////////////////////////////////
+
+struct Sm100MlaPersistentTileScheduler {
+
+  struct Params {
+    int num_blocks;
+    FastDivmod divmod_m_block;
+    FastDivmod divmod_b;
+    FastDivmod divmod_split_kv;
+    KernelHardwareInfo hw_info;
+  };
+
+  int block_idx = 0;
+  Params params;
+
+  CUTLASS_DEVICE
+  Sm100MlaPersistentTileScheduler(Params const& params) : block_idx(blockIdx.x), params(params) {}
+
+  template<class ProblemShape, class ClusterShape>
+  static Params to_underlying_arguments(
+      ProblemShape const& problem_shape, KernelHardwareInfo hw_info,
+      ClusterShape const& cluster_shape, int const& split_kv) {
+    using namespace cute;
+    // Get SM count if needed, otherwise use user supplied SM count
+    int sm_count = hw_info.sm_count;
+    if (sm_count <= 1 || sm_count % size<0>(cluster_shape) != 0) {
+      CUTLASS_TRACE_HOST("  WARNING: Arguments do not include a valid SM count.\n"
+          "  For optimal performance, populate the arguments KernelHardwareInfo struct with the SM count.");
+      sm_count = KernelHardwareInfo::query_device_multiprocessor_count(hw_info.device_id);
+    }
+
+    CUTLASS_TRACE_HOST("to_underlying_arguments(): Setting persistent grid SM count to " << sm_count);
+    hw_info.sm_count = sm_count;
+
+    int num_m_blocks = size<0>(cluster_shape);
+    int num_blocks = num_m_blocks * get<3>(problem_shape)  /* Batch */;
+    num_blocks *= split_kv; /* Maximum Split KV*/
+
+    return Params {
+      num_blocks,
+      { num_m_blocks}, { get<3>(problem_shape) }, {split_kv},
+      hw_info
+    };
+  }
+
+  static dim3 get_grid_shape(Params const& params) {
+    dim3 grid(std::min(params.num_blocks, params.hw_info.sm_count), 1, 1);
+    return grid;
+  }
+
+  CUTLASS_DEVICE
+  bool is_valid() {
+    return block_idx < params.num_blocks;
+  }
+
+  CUTLASS_DEVICE
+  auto get_block_coord() {
+    using namespace cute;
+    int block_decode = block_idx;
+    int m_block, bidb, n_split_kv;
+    params.divmod_m_block(block_decode, m_block, block_decode);
+    params.divmod_b(block_decode, bidb, block_decode);
+    params.divmod_split_kv(block_decode, n_split_kv, block_decode);
+    return make_coord(m_block, _0{}, bidb, n_split_kv);
+  }
+
+  CUTLASS_DEVICE
+  Sm100MlaPersistentTileScheduler& operator++() {
+    block_idx += gridDim.x;
+    return *this;
+  }
+};
+
+////////////////////////////////////////////////////////////////////////////////
+
+} // namespace cutlass::fmha::kernel

csrc/attention/mla/sm100_cutlass_mla_kernel.cu

+/*
+Copyright (c) 2025, NVIDIA CORPORATION.  All rights reserved.
+Copyright 2025 SGLang Team. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+/*
+ * Taken from SGLANG PR https://github.com/sgl-project/sglang/pull/6929
+ * by Alcanderian JieXin Liang
+ */
+
+#include <ATen/cuda/CUDAContext.h>
+#include <c10/cuda/CUDAGuard.h>
+#include <cutlass/cutlass.h>
+#include <cutlass/kernel_hardware_info.h>
+#include <torch/all.h>
+
+#include <cute/tensor.hpp>
+#include <iostream>
+
+#include "cutlass_sm100_mla/device/sm100_mla.hpp"
+#include "cutlass_sm100_mla/kernel/sm100_mla_tile_scheduler.hpp"
+
+// clang-format off
+#if !defined(CUDA_VERSION) || CUDA_VERSION < 12040
+void sm100_cutlass_mla_decode(
+    torch::Tensor const& out,
+    torch::Tensor const& q_nope,
+    torch::Tensor const& q_pe,
+    torch::Tensor const& kv_c_and_k_pe_cache,
+    torch::Tensor const& seq_lens,
+    torch::Tensor const& page_table,
+    torch::Tensor const& workspace,
+    int64_t num_kv_splits) {
+  TORCH_CHECK(false, "CUDA version must be >= 12.4 for cutlass_mla_decode");
+}
+int64_t sm100_cutlass_mla_get_workspace_size(int64_t max_seq_len, int64_t num_batches, int64_t sm_count, int64_t num_kv_splits) {
+  TORCH_CHECK(false, "CUDA version must be >= 12.4 for cutlass_mla_get_workspace_size");
+}
+#else
+
+#define CUTLASS_CHECK(status)                                                       \
+  {                                                                                 \
+    cutlass::Status error = status;                                                 \
+    TORCH_CHECK(error == cutlass::Status::kSuccess, cutlassGetStatusString(error)); \
+  }
+
+using namespace cute;
+using namespace cutlass::fmha::kernel;
+
+template <bool v>
+struct IsPersistent {
+  static const bool value = v;
+};
+
+template <typename T, bool IsPaged128, typename PersistenceOption = IsPersistent<true>>
+struct MlaSm100 {
+  using Element = T;
+  using ElementAcc = float;
+  using ElementOut = T;
+
+  using TileShape = Shape<_128, _128, Shape<_512, _64>>;
+  using TileShapeH = cute::tuple_element_t<0, TileShape>;
+  using TileShapeD = cute::tuple_element_t<2, TileShape>;
+
+  // H K (D_latent D_rope) B
+  using ProblemShape = cute::tuple<TileShapeH, int, TileShapeD, int>;
+
+  using StrideQ = cute::tuple<int64_t, _1, int64_t>;  // H D B
+  using StrideK = cute::tuple<int64_t, _1, int64_t>;  // K D B
+  using StrideO = StrideK;                            // H D B
+  using StrideLSE = cute::tuple<_1, int>;             // H B
+
+  using TileScheduler =
+      std::conditional_t<PersistenceOption::value, Sm100MlaPersistentTileScheduler, Sm100MlaIndividualTileScheduler>;
+
+  using FmhaKernel = cutlass::fmha::kernel::Sm100FmhaMlaKernelTmaWarpspecialized<
+      TileShape,
+      Element,
+      ElementAcc,
+      ElementOut,
+      ElementAcc,
+      TileScheduler,
+      /*kIsCpAsync=*/!IsPaged128>;
+  using Fmha = cutlass::fmha::device::MLA<FmhaKernel>;
+};
+
+template <typename T>
+typename T::Fmha::Arguments args_from_options(
+    at::Tensor const& out,
+    at::Tensor const& q_nope,
+    at::Tensor const& q_pe,
+    at::Tensor const& kv_c_and_k_pe_cache,
+    at::Tensor const& seq_lens,
+    at::Tensor const& page_table,
+    double sm_scale,
+    int64_t num_kv_splits) {
+  cutlass::KernelHardwareInfo hw_info;
+  hw_info.device_id = q_nope.device().index();
+  hw_info.sm_count = cutlass::KernelHardwareInfo::query_device_multiprocessor_count(hw_info.device_id);
+
+  int batches = q_nope.sizes()[0];
+  int page_count_per_seq = page_table.sizes()[1];
+  int page_count_total = kv_c_and_k_pe_cache.sizes()[0];
+  int page_size = kv_c_and_k_pe_cache.sizes()[1];
+  int max_seq_len = page_size * page_count_per_seq;
+  using TileShapeH = typename T::TileShapeH;
+  using TileShapeD = typename T::TileShapeD;
+  auto problem_shape = cute::make_tuple(TileShapeH{}, max_seq_len, TileShapeD{}, batches);
+
+  auto [H, K, D, B] = problem_shape;
+  auto [D_latent, D_rope] = D;
+
+  float scale = float(sm_scale);
+
+  using StrideQ = typename T::StrideQ;
+  using StrideK = typename T::StrideK;
+  using StrideO = typename T::StrideO;
+  using StrideLSE = typename T::StrideLSE;
+
+  StrideQ stride_Q_nope = cute::make_tuple(
+      static_cast<int64_t>(q_nope.stride(1)), _1{}, static_cast<int64_t>(q_nope.stride(0)));
+  StrideQ stride_Q_pe = cute::make_tuple(
+      static_cast<int64_t>(q_pe.stride(1)), _1{}, static_cast<int64_t>(q_pe.stride(0)));
+
+  StrideK stride_C = cute::make_tuple(
+      static_cast<int64_t>(0 + D_latent + D_rope), _1{}, static_cast<int64_t>(page_size * (D_latent + D_rope)));
+  StrideLSE stride_PT = cute::make_stride(_1{}, page_count_per_seq);
+  StrideLSE stride_LSE = cute::make_tuple(_1{}, 0 + H);
+  StrideO stride_O = cute::make_tuple(static_cast<int64_t>(0 + D_latent), _1{}, static_cast<int64_t>(0 + H * D_latent));
+
+  using Element = typename T::Element;
+  using ElementOut = typename T::ElementOut;
+  using ElementAcc = typename T::ElementAcc;
+  auto Q_nope_ptr = static_cast<Element*>(q_nope.data_ptr());
+  auto Q_pe_ptr = static_cast<Element*>(q_pe.data_ptr());
+  auto C_ptr = static_cast<Element*>(kv_c_and_k_pe_cache.data_ptr());
+  typename T::Fmha::Arguments arguments{
+      problem_shape,
+      {scale,
+       Q_nope_ptr,
+       stride_Q_nope,
+       Q_pe_ptr,
+       stride_Q_pe,
+       C_ptr,
+       stride_C,
+       C_ptr + D_latent,
+       stride_C,
+       static_cast<int*>(seq_lens.data_ptr()),
+       static_cast<int*>(page_table.data_ptr()),
+       stride_PT,
+       page_count_total,
+       page_size},
+      {static_cast<ElementOut*>(out.data_ptr()), stride_O, static_cast<ElementAcc*>(nullptr), stride_LSE},
+      hw_info,
+      // TODO(trevor-m): Change split_kv back to -1 when
+      // https://github.com/NVIDIA/cutlass/issues/2274 is fixed. Split_kv=1 will
+      // perform worse with larger context length and smaller batch sizes.
+      num_kv_splits, // split_kv
+      nullptr,       // is_var_split_kv
+  };
+  // TODO(kaixih@nvidia): When split_kv=-1 and is_var_split_kv=false, we compute
+  // split_kv automatically based on batch size and sequence length to balance
+  // workload across available SMs. Consider using var_split_kv for manual
+  // control if needed.
+  T::Fmha::set_split_kv(arguments);
+  return arguments;
+}
+
+template <typename Element, bool IsPaged128, typename PersistenceOption>
+void runMla(
+    at::Tensor const& out,
+    at::Tensor const& q_nope,
+    at::Tensor const& q_pe,
+    at::Tensor const& kv_c_and_k_pe_cache,
+    at::Tensor const& seq_lens,
+    at::Tensor const& page_table,
+    at::Tensor const& workspace,
+    double sm_scale,
+    int64_t num_kv_splits,
+    cudaStream_t stream) {
+  using MlaSm100Type = MlaSm100<Element, IsPaged128, PersistenceOption>;
+  typename MlaSm100Type::Fmha fmha;
+  auto arguments = args_from_options<MlaSm100Type>(out, q_nope, q_pe, kv_c_and_k_pe_cache, seq_lens, page_table, sm_scale, num_kv_splits);
+
+  CUTLASS_CHECK(fmha.can_implement(arguments));
+
+  CUTLASS_CHECK(fmha.initialize(arguments, workspace.data_ptr(), stream));
+
+  CUTLASS_CHECK(fmha.run(arguments, workspace.data_ptr(), stream));
+}
+
+#define DISPATCH_BOOL(expr, const_expr, ...) \
+  [&]() -> bool {                            \
+    if (expr) {                              \
+      constexpr bool const_expr = true;      \
+      return __VA_ARGS__();                  \
+    } else {                                 \
+      constexpr bool const_expr = false;     \
+      return __VA_ARGS__();                  \
+    }                                        \
+  }()
+
+void sm100_cutlass_mla_decode(
+    torch::Tensor const& out,
+    torch::Tensor const& q_nope,
+    torch::Tensor const& q_pe,
+    torch::Tensor const& kv_c_and_k_pe_cache,
+    torch::Tensor const& seq_lens,
+    torch::Tensor const& page_table,
+    torch::Tensor const& workspace,
+    double sm_scale,
+    int64_t num_kv_splits) {
+  auto in_dtype = q_nope.dtype();
+  at::cuda::CUDAGuard device_guard{(char)q_nope.get_device()};
+  const cudaStream_t stream = at::cuda::getCurrentCUDAStream(q_nope.get_device());
+  const int page_size = kv_c_and_k_pe_cache.sizes()[1];
+  
+  // NOTE(alcanderian): IsPersistent has bug with manual split_kv.
+  // Kernel will hang if batch is too large with large num_kv_splits. (for example bs=8, num_kv_splits=8)
+  // Maybe per batch split kv will fix this.
+  DISPATCH_BOOL(page_size == 128, IsPaged128, [&] {
+    DISPATCH_BOOL(num_kv_splits <= 1, NotManualSplitKV, [&] {
+      if (in_dtype == at::ScalarType::Half) {
+        runMla<cutlass::half_t, IsPaged128, IsPersistent<NotManualSplitKV>>(
+          out, q_nope, q_pe, kv_c_and_k_pe_cache, seq_lens, page_table, workspace, sm_scale, num_kv_splits, stream);
+      } else if (in_dtype == at::ScalarType::BFloat16) {
+        runMla<cutlass::bfloat16_t, IsPaged128, IsPersistent<NotManualSplitKV>>(
+          out, q_nope, q_pe, kv_c_and_k_pe_cache, seq_lens, page_table, workspace, sm_scale, num_kv_splits, stream);
+      } else if (in_dtype == at::ScalarType::Float8_e4m3fn) {
+        runMla<cutlass::float_e4m3_t, IsPaged128, IsPersistent<NotManualSplitKV>>(
+          out, q_nope, q_pe, kv_c_and_k_pe_cache, seq_lens, page_table, workspace, sm_scale, num_kv_splits, stream);
+      } else {
+        TORCH_CHECK(false, "Unsupported input data type of MLA");
+      }
+      return true;
+    });
+    return true;
+  });
+}
+
+int64_t sm100_cutlass_mla_get_workspace_size(int64_t max_seq_len, int64_t num_batches, int64_t sm_count, int64_t num_kv_splits) {
+  // Workspace size depends on ElementAcc and ElementLSE (same as ElementAcc)
+  // which are float, so Element type here doesn't matter.
+  using MlaSm100Type = MlaSm100<cutlass::half_t, true>;
+
+  // Get split kv. Requires problem shape and sm_count only.
+  typename MlaSm100Type::Fmha::Arguments arguments;
+  using TileShapeH = typename MlaSm100Type::TileShapeH;
+  using TileShapeD = typename MlaSm100Type::TileShapeD;
+  arguments.problem_shape =
+      cute::make_tuple(TileShapeH{}, static_cast<int>(max_seq_len), TileShapeD{}, static_cast<int>(num_batches));
+  // Assumes device 0 when getting sm_count.
+  arguments.hw_info.sm_count =
+      sm_count <= 0 ? cutlass::KernelHardwareInfo::query_device_multiprocessor_count(/*device_id=*/0) : sm_count;
+  arguments.split_kv = num_kv_splits;
+  MlaSm100Type::Fmha::set_split_kv(arguments);
+
+  return MlaSm100Type::Fmha::get_workspace_size(arguments);
+}
+
+#endif
+// clang-format on

csrc/ops.h

@@ -167,6 +167,19 @@ void cutlass_mla_decode(torch::Tensor const& out, torch::Tensor const& q_nope,
                         torch::Tensor const& seq_lens,
                         torch::Tensor const& page_table, double scale);
 
+void sm100_cutlass_mla_decode(
+    torch::Tensor const& out, torch::Tensor const& q_nope,
+    torch::Tensor const& q_pe, torch::Tensor const& kv_c_and_k_pe_cache,
+    torch::Tensor const& seq_lens, torch::Tensor const& page_table,
+    torch::Tensor const& workspace, double sm_scale,
+    int64_t num_kv_splits =
+        1 /* Set to 1 to avoid cuda_graph issue by default. */);
+
+int64_t sm100_cutlass_mla_get_workspace_size(
+    int64_t max_seq_len, int64_t num_batches, int64_t sm_count = 0,
+    int64_t num_kv_splits =
+        1 /* Set to 1 to avoid cuda_graph issue by default. */);
+
 torch::Tensor get_cuda_view_from_cpu_tensor(torch::Tensor& cpu_tensor);
 
 #ifndef USE_ROCM

csrc/torch_bindings.cpp

@@ -514,6 +514,23 @@ TORCH_LIBRARY_EXPAND(TORCH_EXTENSION_NAME, ops) {
       "                   Tensor page_table, float scale) -> ()");
   ops.impl("cutlass_mla_decode", torch::kCUDA, &cutlass_mla_decode);
 
+  // SM100 CUTLASS MLA decode
+  ops.def(
+      "sm100_cutlass_mla_decode(Tensor! out, Tensor q_nope, Tensor q_pe,"
+      "                         Tensor kv_c_and_k_pe_cache, Tensor seq_lens,"
+      "                         Tensor page_table, Tensor workspace, float "
+      "scale,"
+      "                         int num_kv_splits) -> ()");
+  ops.impl("sm100_cutlass_mla_decode", torch::kCUDA, &sm100_cutlass_mla_decode);
+
+  // SM100 CUTLASS MLA workspace
+  ops.def(
+      "sm100_cutlass_mla_get_workspace_size(int max_seq_len, int num_batches,"
+      "                                     int sm_count, int num_kv_splits) "
+      "-> int");
+  ops.impl("sm100_cutlass_mla_get_workspace_size",
+           &sm100_cutlass_mla_get_workspace_size);
+
   // Compute NVFP4 block quantized tensor.
   ops.def(
       "scaled_fp4_quant(Tensor! output, Tensor input,"

vllm/_custom_ops.py

@@ -1843,6 +1843,26 @@ def cutlass_mla_decode(out: torch.Tensor, q_nope: torch.Tensor,
     return out
 
 
+def sm100_cutlass_mla_decode(out: torch.Tensor, q_nope: torch.Tensor,
+                             q_pe: torch.Tensor,
+                             kv_c_and_k_pe_cache: torch.Tensor,
+                             seq_lens: torch.Tensor, page_table: torch.Tensor,
+                             workspace: torch.Tensor, scale: float,
+                             num_kv_splits: int) -> torch.Tensor:
+    torch.ops._C.sm100_cutlass_mla_decode(out, q_nope, q_pe,
+                                          kv_c_and_k_pe_cache, seq_lens,
+                                          page_table, workspace, scale,
+                                          num_kv_splits)
+    return out
+
+
+def sm100_cutlass_mla_get_workspace_size(max_seq_len: int, num_batches: int,
+                                         sm_count: int,
+                                         num_kv_splits: int) -> int:
+    return torch.ops._C.sm100_cutlass_mla_get_workspace_size(
+        max_seq_len, num_batches, sm_count, num_kv_splits)
+
+
 if hasattr(torch.ops._C, "weight_packed_linear"):
 
     @register_fake("_C::weight_packed_linear")

vllm/platforms/cuda.py

@@ -166,6 +166,13 @@ class CudaPlatformBase(Platform):
                 logger.info(
                     "Forcing kv cache block size to 64 for FlashMLA backend.")
 
+            use_cutlass_mla = (envs.VLLM_ATTENTION_BACKEND is not None \
+                and envs.VLLM_ATTENTION_BACKEND == "CUTLASS_MLA_VLLM_V1")
+            if use_cutlass_mla and cache_config.block_size != 128:
+                cache_config.block_size = 128
+                logger.info("Forcing kv cache block size to 128 for "
+                            "CUTLASS_MLA_VLLM_V1 backend.")
+
         compilation_config = vllm_config.compilation_config
         if (envs.VLLM_ALL2ALL_BACKEND == "deepep_high_throughput"
                 and parallel_config.data_parallel_size > 1

vllm/v1/attention/backends/mla/common.py

@@ -333,6 +333,9 @@ class MLACommonMetadata(Generic[D]):
     # |-------------------- seq_len ---------------------|
     #                                   |-- query_len ---|
 
+    num_reqs: int
+    max_query_len: int
+
     num_actual_tokens: int  # Number of tokens excluding padding.
     query_start_loc: torch.Tensor
     slot_mapping: torch.Tensor
@@ -716,6 +719,8 @@ class MLACommonMetadataBuilder(AttentionMetadataBuilder[M]):
             )
 
         attn_metadata = self.metadata_cls(
+            num_reqs=common_attn_metadata.num_reqs,
+            max_query_len=common_attn_metadata.max_query_len,
             num_actual_tokens=num_actual_tokens,
             query_start_loc=query_start_loc,
             slot_mapping=slot_mapping,

vllm/v1/attention/backends/mla/cutlass_mla.py

 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 
+import os
 from typing import Any, Optional
 
 import torch
@@ -27,6 +28,41 @@ class CutlassMLABackend(MLACommonBackend):
         return CutlassMLAImpl
 
 
+class SM100Workspace:
+
+    def __init__(self, initial_workspace_size):
+        self._workspace_buf = torch.empty(initial_workspace_size,
+                                          device="cuda",
+                                          dtype=torch.uint8)
+
+        self._block_size = 128  # Forced to 128
+
+        # Pre-compute sm_count to avoid recomputing it. Use device 0 as a proxy
+        # (assumes all devices are similar)
+        properties = torch.cuda.get_device_properties(torch.device("cuda:0"))
+        self._sm_count = properties.multi_processor_count
+
+    def get_buf(self):
+        return self._workspace_buf
+
+    def ensure_size(self, attn_metadata: MLACommonMetadata,
+                    num_kv_splits: int):
+        batch_size = attn_metadata.num_reqs
+        max_seq_len = attn_metadata.max_query_len
+
+        workspace_size = ops.sm100_cutlass_mla_get_workspace_size(
+            max_seq_len * self._block_size,
+            batch_size,
+            self._sm_count,
+            num_kv_splits=num_kv_splits)
+
+        if self._workspace_buf.shape[0] < workspace_size:
+            self._workspace_buf.resize_(workspace_size)
+
+
+g_sm100_workspace = SM100Workspace(128 * 1024 * 1024)  # 128MB
+
+
 class CutlassMLAImpl(MLACommonImpl[MLACommonMetadata]):
 
     def __init__(
@@ -68,7 +104,137 @@ class CutlassMLAImpl(MLACommonImpl[MLACommonMetadata]):
             raise NotImplementedError(
                 "CutlassMLA V1 with FP8 KV cache not yet supported")
 
-    def _forward_decode(
+        self._use_old_cutlass_mla = False
+        force_old_cutlass = os.environ.get("FORCE_OLD_CUTLASS_MLA", None)
+        if force_old_cutlass:
+            logger.warning("Forcing old cutlass mla kernel")
+            self._use_old_cutlass_mla = True
+
+        # TODO: Currently, num_kv_splits is limited to 16 to avoid hanging
+        #       issues. In case the code hangs, use:
+        #       FORCE_NUM_KV_SPLITS=1
+        force_num_kv_splits = os.environ.get("FORCE_NUM_KV_SPLITS", None)
+        if force_num_kv_splits:
+            logger.warning("Forcing num_kv_splits to %d",
+                           int(force_num_kv_splits))
+            self._num_kv_splits = int(force_num_kv_splits)
+        else:
+            self._num_kv_splits = -1  # => Auto-detect
+
+        # Share workspace buffer across all executions
+        self._workspace = g_sm100_workspace
+
+    def _sm100_cutlass_mla_decode(
+        self,
+        q_nope: torch.Tensor,
+        q_pe: torch.Tensor,
+        kv_c_and_k_pe_cache: torch.Tensor,
+        seq_lens: torch.Tensor,
+        page_table: torch.Tensor,
+        workspace: torch.Tensor,
+        sm_scale: float,
+        num_kv_splits: int,
+    ) -> torch.Tensor:
+        assert (q_nope.ndim == 3
+                ), f"q_nope must be a 3D tensor, but got {q_nope.ndim}"
+        assert (
+            q_pe.ndim == 3), f"q_pe must be a 3D tensor, but got {q_pe.ndim}"
+        assert (
+            kv_c_and_k_pe_cache.ndim == 3
+        ), "kv_c_and_k_pe_cache must be a 3D tensor, but got {}".format(
+            kv_c_and_k_pe_cache.ndim)
+
+        B_q, H, D_q_nope = q_nope.shape
+        B_q_2, H_2, D_q_pe = q_pe.shape
+        assert (B_q == B_q_2) and (H == H_2)
+
+        _, PAGE_SIZE, D_ckv = kv_c_and_k_pe_cache.shape
+
+        D_latent = 512
+        D_rope = 64
+        assert D_q_nope == D_latent
+        assert D_q_pe == D_rope
+        assert D_ckv == D_latent + D_rope
+
+        MAX_HEADS = 128
+        assert H <= MAX_HEADS, f"H must be <= {MAX_HEADS}, but got {H}"
+        if H < MAX_HEADS:
+            q_nope_padded = q_nope.new_empty((B_q, MAX_HEADS, D_q_nope))
+            q_nope_padded[:, :H] = q_nope
+            q_nope = q_nope_padded
+
+            q_pe_padded = q_pe.new_empty((B_q, MAX_HEADS, D_q_pe))
+            q_pe_padded[:, :H] = q_pe
+            q_pe = q_pe_padded
+
+        assert len(page_table.shape) == 2
+        B_block_table, block_num = page_table.shape
+        assert B_block_table == B_q
+        assert (block_num
+                > 0), f"block num must be greater than 0, got {block_num}"
+        assert block_num % (128 / PAGE_SIZE) == 0
+
+        # TODO(kaixih@nvidia): support fp8
+        assert q_nope.dtype in (
+            torch.float16,
+            torch.bfloat16,
+        ), f"q_nope.dtype needs to be fp16 or bf16 but got {q_nope.dtype}."
+        assert q_nope.dtype == q_pe.dtype == kv_c_and_k_pe_cache.dtype
+        assert (
+            seq_lens.dtype == torch.int32
+        ), f"seq_lens.dtype needs to be int32 but got {seq_lens.dtype}."
+        assert (
+            page_table.dtype == torch.int32
+        ), f"page_table.dtype needs to be int32 but got {page_table.dtype}."
+
+        out = q_nope.new_empty((B_q, MAX_HEADS, D_latent))
+
+        ops.sm100_cutlass_mla_decode(
+            out,
+            q_nope,
+            q_pe,
+            kv_c_and_k_pe_cache,
+            seq_lens,
+            page_table,
+            workspace,
+            sm_scale,
+            num_kv_splits,
+        )
+        return out[:, :H].contiguous()
+
+    def _sm100_forward_decode(
+        self,
+        q_nope: torch.Tensor,
+        q_pe: torch.Tensor,
+        kv_c_and_k_pe_cache: torch.Tensor,
+        attn_metadata: MLACommonMetadata,
+    ) -> torch.Tensor:
+        assert kv_c_and_k_pe_cache.numel() > 0
+        assert attn_metadata.decode is not None
+
+        if self.kv_cache_dtype.startswith("fp8"):
+            raise NotImplementedError("FP8 Cutlass MLA not yet supported")
+
+        # Adjust workspace size (if necessary)
+        self._workspace.ensure_size(attn_metadata, self._num_kv_splits)
+
+        # Run MLA
+        # Clone q_nope and q_pe to make sure strides computation is correct.
+        # TODO: Check if we really need it
+        q_nope = q_nope.clone()
+        q_pe = q_pe.clone()
+
+        o = self._sm100_cutlass_mla_decode(q_nope, q_pe, kv_c_and_k_pe_cache,
+                                           attn_metadata.decode.seq_lens,
+                                           attn_metadata.decode.block_table,
+                                           self._workspace.get_buf(),
+                                           self.scale, self._num_kv_splits)
+
+        return self._v_up_proj(o)
+
+    # TODO: Currently we leave it here only for backup in case something is
+    #       wrong with the new SM100 CUTLASS MLA kernel
+    def _old_forward_decode(
         self,
         q_nope: torch.Tensor,
         q_pe: torch.Tensor,
@@ -97,3 +263,19 @@ class CutlassMLAImpl(MLACommonImpl[MLACommonMetadata]):
                                attn_metadata.decode.block_table, self.scale)
 
         return self._v_up_proj(o)
+
+    def _forward_decode(
+        self,
+        q_nope: torch.Tensor,
+        q_pe: torch.Tensor,
+        kv_c_and_k_pe_cache: torch.Tensor,
+        attn_metadata: MLACommonMetadata,
+    ) -> torch.Tensor:
+        if self._use_old_cutlass_mla:
+            # TODO: Remove the old cutlass MLA kernel after more extensive
+            #       testing
+            return self._old_forward_decode(q_nope, q_pe, kv_c_and_k_pe_cache,
+                                            attn_metadata)
+
+        return self._sm100_forward_decode(q_nope, q_pe, kv_c_and_k_pe_cache,
+                                          attn_metadata)