[Attention Backend] Add HPC-Ops attention backend (#30540)

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
Co-authored-by: Halcyon <56064364+VAthree@users.noreply.github.com>

docs_new/docs/advanced_features/attention_backend.mdx

@@ -122,6 +122,16 @@ The support matrix is split into two parts: MHA (standard attention) and MLA (mu
       <td style={{padding: "9px 12px", backgroundColor: "rgba(255,255,255,0.02)"}}>❌</td>
       <td style={{padding: "9px 12px", backgroundColor: "rgba(255,255,255,0.05)"}}>❌</td>
     </tr>
+    <tr>
+      <td style={{padding: "9px 12px", fontWeight: 500, backgroundColor: "rgba(255,255,255,0.02)"}}>**HPC-Ops**</td>
+      <td style={{padding: "9px 12px", backgroundColor: "rgba(255,255,255,0.05)"}}>64</td>
+      <td style={{padding: "9px 12px", backgroundColor: "rgba(255,255,255,0.02)"}}>✅</td>
+      <td style={{padding: "9px 12px", backgroundColor: "rgba(255,255,255,0.05)"}}>❌</td>
+      <td style={{padding: "9px 12px", backgroundColor: "rgba(255,255,255,0.02)"}}>❌</td>
+      <td style={{padding: "9px 12px", backgroundColor: "rgba(255,255,255,0.05)"}}>❌</td>
+      <td style={{padding: "9px 12px", backgroundColor: "rgba(255,255,255,0.02)"}}>❌</td>
+      <td style={{padding: "9px 12px", backgroundColor: "rgba(255,255,255,0.05)"}}>❌</td>
+    </tr>
     <tr>
       <td style={{padding: "9px 12px", fontWeight: 500, backgroundColor: "rgba(255,255,255,0.02)"}}>**AITER (ROCm)**</td>
       <td style={{padding: "9px 12px", backgroundColor: "rgba(255,255,255,0.05)"}}>✅</td>
@@ -312,7 +322,7 @@ Speculative decoding topk: `topk` is the number of draft tokens sampled per step
 Page size controls how many tokens are grouped into a KV cache block. For the prefix cache to take effect, the number of tokens must fill at least one complete page. For example, if your prompt is only 32 tokens and `page_size = 64`, it won't fill a complete page and cannot be matched in the prefix cache (pages cannot be padded). With 65 tokens and `page_size = 64`, only the first page of 64 tokens will be cached and matched; the remaining 1 token is discarded. Use `page_size = 1` for maximum prefix reuse (token-level matching). Note that higher page sizes generally improve attention kernel performance, so prefer `page_size > 1` when prefix cache reuse is not critical.
 </Tip>
 
-Many backends that do not natively operate on pages can emulate `page_size > 1` at the wrapper layer by expanding page tables to per-token indices. The "Page Size > 1 (native)" column indicates true in-kernel paging. Some backends require fixed native page sizes and cannot be reduced/emulated differently: TRTLLM MHA (16/32/64), TRTLLM MLA (32/64), CuteDSL MLA (32/64), FlashMLA (64), Cutlass MLA (128), Ascend (128).
+Many backends that do not natively operate on pages can emulate `page_size > 1` at the wrapper layer by expanding page tables to per-token indices. The "Page Size > 1 (native)" column indicates true in-kernel paging. Some backends require fixed native page sizes and cannot be reduced/emulated differently: TRTLLM MHA (16/32/64), TRTLLM MLA (32/64), CuteDSL MLA (32/64), FlashMLA (64), Cutlass MLA (128), Ascend (128), HPC-Ops (64).
 
 MLA page-size constraints:
 - FlashInfer MLA: page_size = 1.
@@ -617,6 +627,27 @@ python3 -m sglang.launch_server \
   --trust-remote-code
 ```
 
+- HPC-Ops (MHA kernels from [HPC-Ops](https://github.com/Tencent/hpc-ops) by the Tencent Hunyuan AI Infra team; Hopper+, requires installing the `hpc` package from source, page size 64, bf16 or fp8_e4m3 KV cache, head_dim 128, q/kv head group 4 or 8)
+```bash Command
+python3 -m sglang.launch_server \
+  --model Qwen/Qwen3-30B-A3B-Instruct-2507-FP8 \
+  --attention-backend hpc_ops \
+  --page-size 64 \
+  --trust-remote-code
+
+# FP8 models should also set --kv-cache-dtype fp8_e4m3 to run the FP8 attention
+# kernels. This enables the fused QKNorm+RoPE+FP8-quant+StoreKV op, which is
+# currently wired for Hunyuan V3 and requires per-rank (q_heads, kv_heads) of
+# (64, 8) or (8, 1), e.g. --tp 1 or --tp 8 for Hy3.
+python3 -m sglang.launch_server \
+  --tp 8 \
+  --model tencent/Hy3-FP8 \
+  --attention-backend hpc_ops \
+  --kv-cache-dtype fp8_e4m3 \
+  --page-size 64 \
+  --trust-remote-code
+```
+
 - FlashAttention 4 (MHA & MLA)
 ```bash Command
 # FA4 for both prefill and decode on SM90/SM100

python/sglang/srt/arg_groups/overrides.py

@@ -1737,6 +1737,16 @@ def _mla_backend_page_constraints(view: Any) -> dict:
                 f"TensorRT-LLM MHA only supports page_size of 16, 32 or 64, changing page_size from {page_size} to 64."
             )
             page_size = 64
+    if (
+        view.attention_backend == "hpc_ops"
+        or view.decode_attention_backend == "hpc_ops"
+        or view.prefill_attention_backend == "hpc_ops"
+    ):
+        if page_size != 64:
+            logger.warning(
+                f"HPC-Ops attention only supports a page_size of 64, changing page_size from {page_size} to 64."
+            )
+            page_size = 64
     if page_size != view.page_size:
         return {"page_size": page_size}
     return {}

python/sglang/srt/layers/attention/attention_registry.py

@@ -244,6 +244,23 @@ def create_trtllm_mha_backend(runner):
     return TRTLLMHAAttnBackend(runner)
 
 
+@register_attention_backend("hpc_ops")
+def create_hpc_ops_backend(runner):
+    if runner.use_mla_backend:
+        raise ValueError("hpc_ops backend can only be used with non-MLA models.")
+    if runner.model_config.is_encoder_decoder:
+        raise ValueError(
+            "Cross attention is not supported in the hpc_ops attention backend."
+        )
+    if runner.server_args.speculative_algorithm is not None:
+        raise ValueError(
+            "hpc_ops backend does not support speculative decoding for now."
+        )
+    from sglang.srt.layers.attention.hpc_ops_backend import HPCOpsAttnBackend
+
+    return HPCOpsAttnBackend(runner)
+
+
 @register_attention_backend("intel_amx")
 def create_intel_amx_backend(runner):
     from sglang.srt.layers.attention.intel_amx_backend import IntelAMXAttnBackend

python/sglang/srt/layers/attention/hpc_ops_backend.py

@@ -0,0 +1,674 @@
+from __future__ import annotations
+
+"""
+Attention backend powered by HPC-Ops (https://github.com/Tencent/hpc-ops),
+a production-grade operator library for LLM inference developed by the
+Tencent Hunyuan AI Infra team.
+
+The backend wraps the paged MHA kernels ``attention_with_kvcache_prefill_bf16``
+(extend) and ``attention_decode_bf16`` (decode). It reads the SGLang
+token-major KV pool as a paged NHD cache ``(num_pages, page_size, num_kv_heads,
+head_dim)`` without any copy, so the only hard requirements are the kernel
+constraints:
+
+- NVIDIA Hopper or newer (sm90+)
+- ``--page-size 64``
+- bf16 model dtype; bf16 or fp8_e4m3 KV cache (the FP8 path additionally
+  requires the model to run the fused QKNorm+RoPE+quant+StoreKV op via
+  ``fused_qk_rope_store_kv_fp8`` — wired for HunYuan V3)
+- head_dim == 128 and num_q_heads // num_kv_heads in {4, 8}
+- default softmax scaling (``head_dim ** -0.5``), no sliding window,
+  no logit cap, decoder-only attention
+
+Note that the HPC-Ops kernels are currently tuned primarily for H20: on other
+GPUs (H100/H200/B200, ...) the speedup over the default attention backend may
+be limited or absent.
+
+Enable it explicitly with ``--attention-backend hpc_ops``.
+"""
+
+import functools
+import importlib.util
+from typing import TYPE_CHECKING, Optional
+
+import msgspec
+import torch
+
+from sglang.kernels.ops.kvcache.trtllm_mha_graph_metadata import (
+    update_trtllm_mha_graph_metadata,
+)
+from sglang.kernels.ops.kvcache.trtllm_mha_page_table import (
+    build_trtllm_mha_page_table,
+)
+from sglang.srt.compilation.compilation_config import register_split_op
+from sglang.srt.layers.attention.base_attn_backend import AttentionBackend
+from sglang.srt.mem_cache.memory_pool import KVWriteLoc
+from sglang.srt.model_executor.forward_batch_info import ForwardBatch
+from sglang.srt.model_executor.forward_context import get_attn_backend
+from sglang.srt.model_executor.runner_backend_utils.breakable_cuda_graph import (
+    eager_on_graph,
+    is_in_breakable_cuda_graph,
+)
+from sglang.srt.model_executor.runner_backend_utils.tc_piecewise_cuda_graph import (
+    get_tc_piecewise_forward_context,
+)
+from sglang.srt.utils.custom_op import register_custom_op
+
+if TYPE_CHECKING:
+    from sglang.srt.layers.radix_attention import RadixAttention
+    from sglang.srt.model_executor.model_runner import ModelRunner
+
+# (num_q_heads // num_kv_heads) values supported by the HPC-Ops MHA kernels.
+_SUPPORTED_GQA_GROUP_SIZES = (4, 8)
+_SUPPORTED_HEAD_DIM = 128
+_REQUIRED_PAGE_SIZE = 64
+# The fused QKNorm+RoPE+FP8-quant+StoreKV kernel is specialized per
+# (num_q_heads, num_kv_heads); only these shard shapes exist today.
+FP8_ROPE_SUPPORTED_HEAD_CONFIGS = ((8, 1), (64, 8))
+# Minimum tokens each SM processes per task in the dynamic-scheduled decode
+# path (matches the HPC-Ops default).
+_FP8_DYNAMIC_SCHED_MIN_PROCESS_LEN = 512
+
+
+@functools.cache
+def has_hpc_ops() -> bool:
+    """Return True if the ``hpc`` package (HPC-Ops) is installed."""
+    return importlib.util.find_spec("hpc") is not None
+
+
+class HPCOpsMetadata(msgspec.Struct):
+    """Per-forward-batch metadata consumed by the HPC-Ops kernels."""
+
+    # KV cache length per request (including tokens written this iteration).
+    # shape: [batch_size], int32
+    cache_seqlens_int32: Optional[torch.Tensor] = None
+    # Cumulative query lengths, extend mode only. shape: [batch_size + 1], int32
+    cu_seqlens_q: Optional[torch.Tensor] = None
+    # Cumulative KV lengths. Only used as a scratch output of the fused
+    # cuda-graph metadata kernel. shape: [batch_size + 1], int32
+    cu_seqlens_k: Optional[torch.Tensor] = None
+    # Paged KV block table. shape: [batch_size, max_num_pages], int32
+    page_table: Optional[torch.Tensor] = None
+    # Maximum query length among the batch (1 for decode).
+    max_seq_len_q: int = 1
+
+    # --- FP8 pass-through fields ---
+    # Written by fused_qk_rope_store_kv_fp8() and consumed by the attention
+    # call of the same layer (the fused RoPE op runs right before attention,
+    # so the fields always hold the current layer's scales).
+    # Dynamic per-token-per-head Q scale.
+    # shape: extend [bs, num_q_heads, max_seq_len_q_pad128]; decode [tokens, num_q_heads]
+    hpc_q_scale: Optional[torch.Tensor] = None
+    # Split-K flag tensor for FP8 decode. shape: [bs, num_kv_heads], int32
+    hpc_split_k_flag: Optional[torch.Tensor] = None
+    # Pre-scheduled decode task map (dynamic-scheduled FP8 decode); None falls
+    # back to the kernel's static split-K scheduling.
+    hpc_task_map: Optional[torch.Tensor] = None
+
+
+class HPCOpsAttnBackend(AttentionBackend):
+    """HPC-Ops paged MHA attention backend (bf16 or fp8_e4m3 KV cache)."""
+
+    # The page table is built on-device from seq_lens, so the D2H sync for
+    # seq_lens_cpu is not needed (same as trtllm_mha / triton).
+    needs_cpu_seq_lens: bool = False
+
+    def __init__(self, model_runner: ModelRunner):
+        super().__init__()
+
+        if not has_hpc_ops():
+            raise ImportError(
+                "The hpc_ops attention backend requires the `hpc` package. "
+                "Install it from https://github.com/Tencent/hpc-ops"
+            )
+
+        if model_runner.spec_algorithm.is_speculative():
+            raise ValueError(
+                "The hpc_ops attention backend does not support speculative "
+                "decoding (MTP/EAGLE) yet."
+            )
+
+        self.page_size = model_runner.page_size
+        if self.page_size != _REQUIRED_PAGE_SIZE:
+            raise ValueError(
+                f"The hpc_ops attention backend requires --page-size "
+                f"{_REQUIRED_PAGE_SIZE}, got {self.page_size}."
+            )
+        if model_runner.kv_cache_dtype not in (torch.bfloat16, torch.float8_e4m3fn):
+            raise ValueError(
+                "The hpc_ops attention backend only supports bf16 or fp8_e4m3 "
+                f"KV cache, got {model_runner.kv_cache_dtype}."
+            )
+        # The FP8 path needs per-token-per-head Q scales that only the fused
+        # HPC-Ops QKNorm+RoPE+quant+StoreKV op produces, so it requires the
+        # model to call fused_qk_rope_store_kv_fp8() (wired for HunYuan V3).
+        self.use_fp8 = model_runner.kv_cache_dtype == torch.float8_e4m3fn
+        if self.use_fp8:
+            heads = (
+                model_runner.model_config.num_attention_heads
+                // model_runner.ps.tp_size,
+                model_runner.model_config.get_num_kv_heads(model_runner.ps.tp_size),
+            )
+            if heads not in FP8_ROPE_SUPPORTED_HEAD_CONFIGS:
+                raise ValueError(
+                    "The hpc_ops FP8 KV cache path requires per-rank "
+                    f"(num_q_heads, num_kv_heads) in "
+                    f"{FP8_ROPE_SUPPORTED_HEAD_CONFIGS} (the fused RoPE+quant "
+                    f"kernel is specialized per shape), got {heads}. Adjust "
+                    "--tp accordingly or use --kv-cache-dtype bfloat16."
+                )
+
+        config = model_runner.model_config
+        head_dim = config.head_dim
+        num_q_heads = config.num_attention_heads // model_runner.ps.tp_size
+        num_kv_heads = config.get_num_kv_heads(model_runner.ps.tp_size)
+        gqa_group_size = num_q_heads // num_kv_heads
+        if head_dim != _SUPPORTED_HEAD_DIM or gqa_group_size not in (
+            _SUPPORTED_GQA_GROUP_SIZES
+        ):
+            raise ValueError(
+                "The hpc_ops attention backend requires head_dim == "
+                f"{_SUPPORTED_HEAD_DIM} and num_q_heads // num_kv_heads in "
+                f"{_SUPPORTED_GQA_GROUP_SIZES}, got head_dim={head_dim}, "
+                f"num_q_heads={num_q_heads}, num_kv_heads={num_kv_heads}."
+            )
+
+        self.max_context_len = model_runner.model_config.context_len
+        self.max_num_pages = (
+            self.max_context_len + self.page_size - 1
+        ) // self.page_size
+        self.device = model_runner.device
+        self.req_to_token = model_runner.req_to_token_pool.req_to_token
+        self.token_to_kv_pool = model_runner.token_to_kv_pool
+
+        # Per-request query prefix sums [0, 1, ..., bs] for the FP8 fused RoPE
+        # op in decode mode; a static buffer so it is CUDA-graph friendly.
+        self._decode_qo_indptr = torch.arange(
+            model_runner.req_to_token_pool.size + 1,
+            dtype=torch.int32,
+            device=self.device,
+        )
+        # Fallback per-tensor KV scale for checkpoints without kv scales.
+        self._ones_scale = torch.ones(1, dtype=torch.float32, device=self.device)
+
+        # Dynamic-scheduled FP8 decode: the task workspace is sized by the
+        # decode CUDA-graph max batch size in init_cuda_graph_state (sizing it
+        # by the full request-pool capacity would cost hundreds of MB); eager
+        # decode batches beyond that fall back to static split-K.
+        self.num_kv_heads = num_kv_heads
+        self._fp8_task_map: Optional[torch.Tensor] = None
+        self._fp8_task_map_max_bs = 0
+
+        # CUDA graph state (allocated in init_cuda_graph_state).
+        self.decode_cuda_graph_metadata = {}
+
+        self.forward_metadata: Optional[HPCOpsMetadata] = None
+
+    def init_forward_metadata(self, forward_batch: ForwardBatch):
+        """Build metadata for the eager (non-CUDA-graph) path."""
+        batch_size = forward_batch.batch_size
+        device = forward_batch.seq_lens.device
+
+        metadata = HPCOpsMetadata()
+        metadata.cache_seqlens_int32 = forward_batch.seq_lens.to(torch.int32)
+
+        if forward_batch.forward_mode.is_decode_or_idle():
+            metadata.max_seq_len_q = 1
+        else:
+            assert forward_batch.forward_mode.is_extend(), (
+                "The hpc_ops attention backend does not support forward mode "
+                f"{forward_batch.forward_mode}."
+            )
+            max_q = max(forward_batch.extend_seq_lens_cpu)
+            metadata.max_seq_len_q = (
+                int(max_q.item()) if isinstance(max_q, torch.Tensor) else int(max_q)
+            )
+            metadata.cu_seqlens_q = torch.nn.functional.pad(
+                torch.cumsum(forward_batch.extend_seq_lens, dim=0, dtype=torch.int32),
+                (1, 0),
+            )
+
+        metadata.page_table = torch.empty(
+            (batch_size, self.max_num_pages), dtype=torch.int32, device=device
+        )
+        build_trtllm_mha_page_table(
+            req_to_token=self.req_to_token,
+            req_pool_indices=forward_batch.req_pool_indices,
+            cache_seqlens=metadata.cache_seqlens_int32,
+            page_table=metadata.page_table,
+            page_size=self.page_size,
+        )
+        if (
+            self.use_fp8
+            and self._fp8_task_map is not None
+            and forward_batch.forward_mode.is_decode()
+            and batch_size <= self._fp8_task_map_max_bs
+        ):
+            metadata.hpc_task_map = self._assign_fp8_decode_tasks(
+                metadata.cache_seqlens_int32
+            )
+        self.forward_metadata = metadata
+
+    def init_cuda_graph_state(self, max_bs: int, max_num_tokens: int):
+        if self.use_fp8:
+            import hpc
+
+            self._fp8_task_map = hpc.get_attention_decode_task_workspace(
+                max_bs,
+                self.max_context_len,
+                self.num_kv_heads,
+                min_process_len=_FP8_DYNAMIC_SCHED_MIN_PROCESS_LEN,
+            )
+            self._fp8_task_map_max_bs = max_bs
+
+        self.decode_cuda_graph_metadata = {
+            "cache_seqlens": torch.zeros(max_bs, dtype=torch.int32, device=self.device),
+            "cu_seqlens_k": torch.zeros(
+                max_bs + 1, dtype=torch.int32, device=self.device
+            ),
+            "page_table": torch.zeros(
+                max_bs, self.max_num_pages, dtype=torch.int32, device=self.device
+            ),
+        }
+
+    def init_forward_metadata_out_graph(
+        self, forward_batch: ForwardBatch, in_capture: bool = False
+    ):
+        bs = forward_batch.batch_size
+        assert forward_batch.forward_mode.is_decode_or_idle(), (
+            "The hpc_ops attention backend only supports CUDA graphs for "
+            f"normal decode, got {forward_batch.forward_mode}."
+        )
+        if in_capture:
+            metadata = HPCOpsMetadata()
+            metadata.cache_seqlens_int32 = self.decode_cuda_graph_metadata[
+                "cache_seqlens"
+            ][:bs]
+            metadata.cu_seqlens_k = self.decode_cuda_graph_metadata["cu_seqlens_k"][
+                : bs + 1
+            ]
+            metadata.page_table = self.decode_cuda_graph_metadata["page_table"][:bs, :]
+            metadata.max_seq_len_q = 1
+            self.decode_cuda_graph_metadata[bs] = metadata
+
+        self.forward_metadata = self.decode_cuda_graph_metadata[bs]
+
+    def init_forward_metadata_in_graph(self, forward_batch: ForwardBatch):
+        """Rebuild cache_seqlens and the page table on-device (graph-recordable)."""
+        bs = forward_batch.batch_size
+        metadata = self.decode_cuda_graph_metadata[bs]
+        update_trtllm_mha_graph_metadata(
+            req_pool_indices=forward_batch.req_pool_indices[:bs],
+            seq_lens=forward_batch.seq_lens[:bs],
+            req_to_token=self.req_to_token,
+            cache_seqlens=metadata.cache_seqlens_int32,
+            cu_seqlens_k=metadata.cu_seqlens_k,
+            page_table=metadata.page_table,
+            bs=bs,
+            seqlen_offset=0,
+            max_seq_pages=self.max_num_pages,
+            page_size=self.page_size,
+        )
+        if self.use_fp8 and self._fp8_task_map is not None:
+            # Recorded into the decode graph, so the task map is re-populated
+            # from the live seq_lens at every replay.
+            metadata.hpc_task_map = self._assign_fp8_decode_tasks(
+                metadata.cache_seqlens_int32
+            )
+        self.forward_metadata = metadata
+
+    def get_cuda_graph_seq_len_fill_value(self) -> int:
+        return 1
+
+    def _check_layer_supported(self, layer: RadixAttention):
+        if layer.sliding_window_size is not None and layer.sliding_window_size > -1:
+            raise ValueError(
+                "The hpc_ops attention backend does not support sliding window."
+            )
+        if layer.logit_cap > 0:
+            raise ValueError(
+                "The hpc_ops attention backend does not support logit cap."
+            )
+        # The HPC-Ops kernels hard-code the softmax scale to head_dim ** -0.5.
+        if abs(layer.scaling - layer.head_dim**-0.5) > 1e-8:
+            raise ValueError(
+                "The hpc_ops attention backend only supports the default "
+                f"softmax scaling head_dim ** -0.5, got {layer.scaling}."
+            )
+
+    def _paged_kv_buffers(self, layer: RadixAttention):
+        k_cache, v_cache = self.token_to_kv_pool.get_kv_buffer(layer.layer_id)
+        k_cache = k_cache.view(-1, self.page_size, layer.tp_k_head_num, layer.head_dim)
+        v_cache = v_cache.view(-1, self.page_size, layer.tp_v_head_num, layer.head_dim)
+        return k_cache, v_cache
+
+    def _layer_kv_scales(self, layer: RadixAttention):
+        """Per-tensor K/V scales as fp32 [1] tensors (ones when absent)."""
+        k_scale = (
+            layer.k_scale.reshape(1).float()
+            if layer.k_scale is not None
+            else self._ones_scale
+        )
+        v_scale = (
+            layer.v_scale.reshape(1).float()
+            if layer.v_scale is not None
+            else self._ones_scale
+        )
+        return k_scale, v_scale
+
+    def fused_qk_rope_store_kv_fp8(
+        self,
+        layer: RadixAttention,
+        forward_batch: ForwardBatch,
+        qkv: torch.Tensor,
+        cos_sin_cache: torch.Tensor,
+        q_norm_weight: Optional[torch.Tensor],
+        k_norm_weight: Optional[torch.Tensor],
+        qk_norm_policy: int,
+    ) -> torch.Tensor:
+        """Fused QKNorm + RoPE + FP8 quant + paged-KV write (FP8 mode only).
+
+        Called by the model layer instead of its own norm/rope/KV-write; the
+        dynamic per-token-per-head Q scale and the split-K flag are stashed in
+        the forward metadata and consumed by the attention call of the same
+        layer. Returns the FP8 query of shape [num_tokens, num_q_heads,
+        head_dim]. The subsequent ``self.attn(...)`` call must pass
+        ``save_kv_cache=False`` (K/V are already written here).
+
+        Under a captured prefill graph (breakable / tc_piecewise) this routes
+        through a graph-splitting op — like attention itself — so the Python
+        Q-scale hand-off between this op and attention stays alive at replay.
+
+        Note: the HPC-Ops RMSNorm hard-codes eps=1e-6; checkpoints with a
+        slightly different rms_norm_eps (e.g. HunYuan V3's 1e-5) accept this
+        approximation, matching the reference HPC-Ops integration.
+        """
+        assert self.use_fp8, "fused_qk_rope_store_kv_fp8 requires fp8 KV cache"
+
+        is_extend = not forward_batch.forward_mode.is_decode_or_idle()
+        out_q = torch.empty(
+            (qkv.shape[0], layer.tp_q_head_num, layer.head_dim),
+            dtype=torch.float8_e4m3fn,
+            device=qkv.device,
+        )
+
+        if is_extend and get_tc_piecewise_forward_context() is not None:
+            # Captured prefill graph: run through the splitting op (eager at
+            # capture AND at replay, keeping the metadata hand-off alive).
+            if is_in_breakable_cuda_graph():
+                breakable_hpc_ops_fp8_rope_store_kv(
+                    qkv,
+                    cos_sin_cache,
+                    out_q,
+                    layer.layer_id,
+                    qk_norm_policy,
+                    q_norm_weight=q_norm_weight,
+                    k_norm_weight=k_norm_weight,
+                )
+            else:
+                hpc_ops_fp8_rope_store_kv(
+                    qkv,
+                    cos_sin_cache,
+                    out_q,
+                    layer.layer_id,
+                    qk_norm_policy,
+                    q_norm_weight=q_norm_weight,
+                    k_norm_weight=k_norm_weight,
+                )
+        else:
+            self._run_fp8_rope_store_kv(
+                layer=layer,
+                forward_batch=forward_batch,
+                qkv=qkv,
+                cos_sin_cache=cos_sin_cache,
+                q_norm_weight=q_norm_weight,
+                k_norm_weight=k_norm_weight,
+                qk_norm_policy=qk_norm_policy,
+                is_extend=is_extend,
+                out_q=out_q,
+            )
+        return out_q
+
+    def _run_fp8_rope_store_kv(
+        self,
+        layer: RadixAttention,
+        forward_batch: Optional[ForwardBatch],
+        qkv: torch.Tensor,
+        cos_sin_cache: torch.Tensor,
+        q_norm_weight: Optional[torch.Tensor],
+        k_norm_weight: Optional[torch.Tensor],
+        qk_norm_policy: int,
+        is_extend: bool,
+        out_q: torch.Tensor,
+    ) -> None:
+        """Invoke the fused kernel and stash the Q scales in the metadata."""
+        import hpc
+
+        metadata = self.forward_metadata
+        k_cache, v_cache = self._paged_kv_buffers(layer)
+        k_scale, v_scale = self._layer_kv_scales(layer)
+
+        if is_extend:
+            q_index = metadata.cu_seqlens_q
+            max_seqlens = metadata.max_seq_len_q
+        else:
+            q_index = self._decode_qo_indptr[: forward_batch.batch_size + 1]
+            max_seqlens = 1
+
+        # QPERTOKEN_PERHEAD_KPERTENSOR_VPERTENSOR: dynamic per-token-per-head
+        # Q quant, static per-tensor K/V quant.
+        quant_policy = hpc.QuantType.QPERTOKEN_PERHEAD_KPERTENSOR_VPERTENSOR.value
+        _, q_scale, split_k_flag = hpc.rope_norm_store_kv_fp8(
+            key_cache=k_cache,
+            value_cache=v_cache,
+            qkv=qkv,
+            cos_sin=cos_sin_cache,
+            num_seqlen_per_req=metadata.cache_seqlens_int32,
+            q_index=q_index,
+            kvcache_indices=metadata.page_table,
+            is_prefill=is_extend,
+            k_scale=k_scale,
+            v_scale=v_scale,
+            quant_policy=quant_policy,
+            max_seqlens=max_seqlens,
+            q_norm_weight=q_norm_weight,
+            k_norm_weight=k_norm_weight,
+            out_q=out_q,
+            qk_norm_policy=qk_norm_policy,
+        )
+        metadata.hpc_q_scale = q_scale
+        metadata.hpc_split_k_flag = split_k_flag
+
+    def _assign_fp8_decode_tasks(self, cache_seqlens: torch.Tensor) -> torch.Tensor:
+        """Populate the dynamic-scheduled decode task map from live KV lengths.
+
+        The scheduler pass bins every (request, kv_head, KV-tile) chunk into
+        per-CTA task lists so each CTA gets roughly equal token work — this is
+        what balances decode batches with skewed sequence lengths.
+        """
+        import hpc
+
+        # NOTE: assign's ``mtp`` means tokens-per-request (>= 1; plain decode
+        # is 1), unlike attention_decode's ``mtp`` which counts extra draft
+        # tokens (plain decode is 0). Passing 0 here makes the scheduler
+        # kernel launch with an invalid configuration.
+        hpc.assign_attention_decode_task(
+            cache_seqlens,
+            self._fp8_task_map,
+            self.num_kv_heads,
+            mtp=1,
+            new_kv_included=True,
+            min_process_len=_FP8_DYNAMIC_SCHED_MIN_PROCESS_LEN,
+        )
+        return self._fp8_task_map
+
+    def _take_fp8_scales(self, metadata: HPCOpsMetadata):
+        """Pop the per-layer FP8 scales written by the fused RoPE op."""
+        q_scale = metadata.hpc_q_scale
+        split_k_flag = metadata.hpc_split_k_flag
+        if q_scale is None:
+            raise RuntimeError(
+                "The hpc_ops attention backend with an fp8_e4m3 KV cache "
+                "requires the model to run the fused HPC-Ops "
+                "QKNorm+RoPE+quant+StoreKV op (fused_qk_rope_store_kv_fp8), "
+                "which produces the per-token-per-head Q scales. This is "
+                "currently wired for HunYuan V3 only; use "
+                "--kv-cache-dtype bfloat16 for other models."
+            )
+        metadata.hpc_q_scale = None
+        metadata.hpc_split_k_flag = None
+        return q_scale, split_k_flag
+
+    def forward_extend(
+        self,
+        q: torch.Tensor,
+        k: torch.Tensor,
+        v: torch.Tensor,
+        layer: RadixAttention,
+        forward_batch: ForwardBatch,
+        save_kv_cache: bool = True,
+        **kwargs,
+    ) -> torch.Tensor:
+        import hpc
+
+        self._check_layer_supported(layer)
+
+        if save_kv_cache and k is not None:
+            self.token_to_kv_pool.set_kv_buffer(
+                layer,
+                KVWriteLoc(forward_batch.out_cache_loc),
+                k,
+                v,
+                layer.k_scale,
+                layer.v_scale,
+            )
+
+        metadata = self.forward_metadata
+        k_cache, v_cache = self._paged_kv_buffers(layer)
+
+        if self.use_fp8:
+            q_scale, _ = self._take_fp8_scales(metadata)
+            k_scale, v_scale = self._layer_kv_scales(layer)
+            o = hpc.attention_with_kvcache_prefill_fp8(
+                q.view(-1, layer.tp_q_head_num, layer.head_dim),
+                k_cache,
+                v_cache,
+                q_scale,
+                k_scale,
+                v_scale,
+                metadata.cu_seqlens_q,
+                metadata.page_table,
+                metadata.cache_seqlens_int32,
+                metadata.max_seq_len_q,
+            )
+        else:
+            o = hpc.attention_with_kvcache_prefill_bf16(
+                q.view(-1, layer.tp_q_head_num, layer.head_dim),
+                k_cache,
+                v_cache,
+                metadata.cu_seqlens_q,
+                metadata.page_table,
+                metadata.cache_seqlens_int32,
+                metadata.max_seq_len_q,
+            )
+        return o.view(-1, layer.tp_q_head_num * layer.head_dim)
+
+    def forward_decode(
+        self,
+        q: torch.Tensor,
+        k: torch.Tensor,
+        v: torch.Tensor,
+        layer: RadixAttention,
+        forward_batch: ForwardBatch,
+        save_kv_cache: bool = True,
+        **kwargs,
+    ) -> torch.Tensor:
+        import hpc
+
+        self._check_layer_supported(layer)
+
+        if save_kv_cache and k is not None:
+            self.token_to_kv_pool.set_kv_buffer(
+                layer,
+                KVWriteLoc(forward_batch.out_cache_loc),
+                k,
+                v,
+                layer.k_scale,
+                layer.v_scale,
+            )
+
+        metadata = self.forward_metadata
+        k_cache, v_cache = self._paged_kv_buffers(layer)
+
+        if self.use_fp8:
+            q_scale, split_k_flag = self._take_fp8_scales(metadata)
+            k_scale, v_scale = self._layer_kv_scales(layer)
+            o = hpc.attention_decode_fp8(
+                q.view(-1, layer.tp_q_head_num, layer.head_dim),
+                k_cache,
+                v_cache,
+                metadata.page_table,
+                metadata.cache_seqlens_int32,
+                q_scale,
+                k_scale,
+                v_scale,
+                mtp=0,
+                new_kv_included=True,
+                splitk=True,
+                task_map=metadata.hpc_task_map,
+                split_flag=split_k_flag,
+            )
+        else:
+            o = hpc.attention_decode_bf16(
+                q.view(-1, layer.tp_q_head_num, layer.head_dim),
+                k_cache,
+                v_cache,
+                metadata.page_table,
+                metadata.cache_seqlens_int32,
+                mtp=0,
+                new_kv_included=True,
+                splitk=True,
+            )
+        return o.view(-1, layer.tp_q_head_num * layer.head_dim)
+
+
+@register_custom_op(mutates_args=["out_q"])
+@register_split_op()
+def hpc_ops_fp8_rope_store_kv(
+    qkv: torch.Tensor,
+    cos_sin_cache: torch.Tensor,
+    out_q: torch.Tensor,
+    layer_id: int,
+    qk_norm_policy: int,
+    *,
+    q_norm_weight: Optional[torch.Tensor] = None,
+    k_norm_weight: Optional[torch.Tensor] = None,
+) -> None:
+    """Graph-splitting wrapper for the fused QKNorm+RoPE+FP8-quant+StoreKV op.
+
+    Like ``unified_attention_with_output``, this runs eagerly between captured
+    prefill-graph segments (at capture and at every replay), so the Python
+    hand-off of the dynamic Q scales to the following attention op stays
+    alive. ``out_q`` is preallocated by the captured segment and mutated in
+    place, which is what stitches the surrounding graph segments together.
+    """
+    context = get_tc_piecewise_forward_context()
+    forward_batch = context.forward_batch
+    attention_layer = context.attention_layers[layer_id]
+    real_num_tokens = forward_batch.num_token_non_padded_cpu
+
+    backend = get_attn_backend()
+    backend._run_fp8_rope_store_kv(
+        layer=attention_layer,
+        forward_batch=forward_batch,
+        qkv=qkv[:real_num_tokens],
+        cos_sin_cache=cos_sin_cache,
+        q_norm_weight=q_norm_weight,
+        k_norm_weight=k_norm_weight,
+        qk_norm_policy=qk_norm_policy,
+        is_extend=True,
+        out_q=out_q[:real_num_tokens],
+    )
+
+
+breakable_hpc_ops_fp8_rope_store_kv = eager_on_graph(True)(hpc_ops_fp8_rope_store_kv)

python/sglang/srt/models/hunyuan_v3.py

@@ -42,6 +42,7 @@ from sglang.srt.layers.vocab_parallel_embedding import (
     VocabParallelEmbedding,
 )
 from sglang.srt.managers.schedule_batch import ForwardBatch
+from sglang.srt.model_executor.forward_context import get_attn_backend
 from sglang.srt.model_executor.runner import get_is_capture_mode
 from sglang.srt.model_loader.weight_utils import default_weight_loader
 from sglang.srt.runtime_context import get_parallel, get_stream
@@ -313,6 +314,35 @@ class HYV3Attention(nn.Module):
             self.q_norm = RMSNorm(self.head_dim, rms_norm_eps)
             self.k_norm = RMSNorm(self.head_dim, rms_norm_eps)
 
+        # HPC-Ops FP8 attention path: the fused QKNorm+RoPE+FP8-quant+StoreKV
+        # op replaces the norm/rope/KV-write below and produces the
+        # per-token-per-head Q scales the FP8 attention kernels require.
+        # Resolved lazily on first forward (None = undecided) because the
+        # attention backend does not exist yet at layer-construction time.
+        self.use_hpc_ops_fp8_attn: Optional[bool] = (
+            None
+            if is_cuda()
+            and self.head_dim == 128
+            and (self.num_heads, self.num_kv_heads) in ((8, 1), (64, 8))
+            else False
+        )
+        self._hpc_cos_sin_fp32: Optional[torch.Tensor] = None
+        self._hpc_q_norm_w_fp32: Optional[torch.Tensor] = None
+        self._hpc_k_norm_w_fp32: Optional[torch.Tensor] = None
+
+    def _resolve_hpc_ops_fp8_attn(self) -> bool:
+        from sglang.srt.layers.attention.hpc_ops_backend import HPCOpsAttnBackend
+
+        backend = get_attn_backend()
+        use_fp8_path = isinstance(backend, HPCOpsAttnBackend) and backend.use_fp8
+        if use_fp8_path:
+            # The fused kernel wants a fp32 cos/sin table and fp32 norm weights.
+            self._hpc_cos_sin_fp32 = self.rotary_emb.cos_sin_cache.float()
+            if self.use_qk_norm:
+                self._hpc_q_norm_w_fp32 = self.q_norm.weight.detach().float()
+                self._hpc_k_norm_w_fp32 = self.k_norm.weight.detach().float()
+        return use_fp8_path
+
     def forward(
         self,
         positions: torch.Tensor,
@@ -320,6 +350,32 @@ class HYV3Attention(nn.Module):
         forward_batch: ForwardBatch,
     ) -> torch.Tensor:
         qkv, _ = self.qkv_proj(hidden_states)
+
+        if self.use_hpc_ops_fp8_attn is None:
+            self.use_hpc_ops_fp8_attn = self._resolve_hpc_ops_fp8_attn()
+        if self.use_hpc_ops_fp8_attn and not forward_batch.forward_mode.is_idle():
+            # HunYuan V3 applies QK-Norm before RoPE -> qk_norm_policy=2.
+            q = get_attn_backend().fused_qk_rope_store_kv_fp8(
+                layer=self.attn,
+                forward_batch=forward_batch,
+                qkv=qkv,
+                cos_sin_cache=self._hpc_cos_sin_fp32,
+                q_norm_weight=self._hpc_q_norm_w_fp32,
+                k_norm_weight=self._hpc_k_norm_w_fp32,
+                qk_norm_policy=2 if self.use_qk_norm else 0,
+            )
+            # q is FP8; RadixAttention.forward sizes the output buffer as
+            # bf16 for fp8 queries.
+            attn_output = self.attn(
+                q.view(-1, self.q_size),
+                None,
+                None,
+                forward_batch,
+                save_kv_cache=False,
+            )
+            output, _ = self.o_proj(attn_output)
+            return output
+
         q, k, v = qkv.split([self.q_size, self.kv_size, self.kv_size], dim=-1)
 
         if self.use_qk_norm:

python/sglang/srt/server_args.py

@@ -211,6 +211,7 @@ ATTENTION_BACKEND_CHOICES = [
     "tokenspeed_mla",
     "trtllm_mha",
     "dual_chunk_flash_attn",
+    "hpc_ops",  # HPC-Ops (https://github.com/Tencent/hpc-ops), Hopper+, requires --page-size 64
     # AMD specific
     "aiter",
     "wave",