---
id: pr-flashinfer-1198
repo: flashinfer-ai/flashinfer
pr: 1198
title: 'bugfix: fix blackwell fmha hanging issue for empty kv_len'
author: yzh119
date: '2025-07-06'
url: https://github.com/flashinfer-ai/flashinfer/pull/1198
source_category: upstream-code
architectures:
- sm100
tags:
- attention
- epilogue-fusion
- flash-attention
- tma
techniques:
- epilogue-fusion
hardware_features:
- tma
kernel_types:
- attention
- flash-attention
languages:
- python
captured_at: '2026-04-17'
status: merged
merge_sha: 3b01face12e6520abdb3ac6ac8a5797ec4521c49
inclusion_reason: kernel file changes
changed_paths:
- include/flashinfer/attention/blackwell/collective/sm100_fmha_fwd_epilogue_tma_warpspecialized.hpp
- include/flashinfer/attention/blackwell/collective/sm100_fmha_fwd_mainloop_tma_warpspecialized.hpp
- include/flashinfer/attention/blackwell/kernel/sm100_fmha_fwd_kernel_tma_warpspecialized.hpp
- tests/test_blackwell_fmha.py
head_ref_oid: 4ef0dce2e71cc361f431ca2144dfae04334e5011
artifact_dir: evidence/pull-bundles/flashinfer/gh-1198
---
# bugfix: fix blackwell fmha hanging issue for empty kv_len

- Repository: `flashinfer-ai/flashinfer`
- PR: [1198](https://github.com/flashinfer-ai/flashinfer/pull/1198)
- Decision: `kernel file changes`
- Reason: kernel file changes

## Changed Paths

- `include/flashinfer/attention/blackwell/collective/sm100_fmha_fwd_epilogue_tma_warpspecialized.hpp`
- `include/flashinfer/attention/blackwell/collective/sm100_fmha_fwd_mainloop_tma_warpspecialized.hpp`
- `include/flashinfer/attention/blackwell/kernel/sm100_fmha_fwd_kernel_tma_warpspecialized.hpp`
- `tests/test_blackwell_fmha.py`

## Evidence Bundle

`evidence/pull-bundles/flashinfer/gh-1198`
