---
id: pr-flashinfer-2959
repo: flashinfer-ai/flashinfer
pr: 2959
title: '[Fmha] Add head_dim=512 support for trtllm attention kernels'
author: djmmoss
date: '2026-04-22'
url: https://github.com/flashinfer-ai/flashinfer/pull/2959
source_category: upstream-code
architectures:
- sm100
tags:
- TMA
- attention_kv
- fp8
- mla
- mxfp4
- nvfp4
- paged attention
techniques:
- async-copy
hardware_features:
- fp4
- fp8
- mxfp4
- nvfp4
- tma
kernel_types:
- attention
- decode
- mla
- reduction
languages:
- cuda-cpp
captured_at: '2026-05-16'
status: merged
merge_sha: 9f7adfb8461d68ef5e18479f61cc6919b7f80c3d
inclusion_reason: Preserve page/KV/layout and plan-run contracts; profile memory traffic separately from math utilization.
changed_paths:
- csrc/fmhaReduction.cu
- flashinfer/artifacts.py
- include/flashinfer/trtllm/fmha/fmhaKernels.cuh
- include/flashinfer/trtllm/fmha/kernelParams.h
- tests/attention/test_trtllm_gen_attention.py
artifact_dir: evidence/pull-bundles/flashinfer/gh-2959
head_ref_oid: 69c901a560a4e5cc11d5ba2c07d2c9e84ac7435f
---
# [Fmha] Add head_dim=512 support for trtllm attention kernels

- Repository: `flashinfer-ai/flashinfer`
- PR: [2959](https://github.com/flashinfer-ai/flashinfer/pull/2959)
- Decision: `Preserve page/KV/layout and plan-run contracts; profile memory traffic separately from math utilization.`
- Reason: Preserve page/KV/layout and plan-run contracts; profile memory traffic separately from math utilization.

## Changed Paths

- `csrc/fmhaReduction.cu`
- `flashinfer/artifacts.py`
- `include/flashinfer/trtllm/fmha/fmhaKernels.cuh`
- `include/flashinfer/trtllm/fmha/kernelParams.h`
- `tests/attention/test_trtllm_gen_attention.py`

## Evidence Bundle

`evidence/pull-bundles/flashinfer/gh-2959`
