---
id: pr-flash-attention-2085
repo: Dao-AILab/flash-attention
pr: 2085
title: Add blocksparse support for bwd on blackwell
author: drisspg
date: '2025-12-18'
url: https://github.com/Dao-AILab/flash-attention/pull/2085
source_category: upstream-code
architectures:
- sm100
tags:
- arch_pipeline
- attention_kv
- benchmark_test
- blackwell
- block sparse
- compiler_runtime
- softmax
techniques:
- async-copy
- pipeline-stages
hardware_features:
- blackwell
- tma
kernel_types:
- attention
- compiler
- runtime
- softmax
languages:
- cute-dsl
captured_at: '2026-05-16'
status: merged
merge_sha: eacbc560be4811b40dee21c4449ab226d40a2edc
inclusion_reason: 'Extract the architecture assumption first: SM target, TMA/WGMMA/tcgen path, cluster use, and pipeline stages.'
changed_paths:
- flash_attn/cute/block_sparse_utils.py
- flash_attn/cute/block_sparsity.py
- flash_attn/cute/flash_bwd_sm100.py
- flash_attn/cute/interface.py
- flash_attn/cute/mask.py
- tests/cute/test_mask_mod.py
- tests/cute/test_score_mod.py
artifact_dir: evidence/pull-bundles/flash-attention/gh-2085
head_ref_oid: 3480fba3e434bf668d4eaf46e740bef5b2957be6
---
# Add blocksparse support for bwd on blackwell

- Repository: `Dao-AILab/flash-attention`
- PR: [2085](https://github.com/Dao-AILab/flash-attention/pull/2085)
- Decision: `Extract the architecture assumption first: SM target, TMA/WGMMA/tcgen path, cluster use, and pipeline stages.`
- Reason: Extract the architecture assumption first: SM target, TMA/WGMMA/tcgen path, cluster use, and pipeline stages.

## Changed Paths

- `flash_attn/cute/block_sparse_utils.py`
- `flash_attn/cute/block_sparsity.py`
- `flash_attn/cute/flash_bwd_sm100.py`
- `flash_attn/cute/interface.py`
- `flash_attn/cute/mask.py`
- `tests/cute/test_mask_mod.py`
- `tests/cute/test_score_mod.py`

## Evidence Bundle

`evidence/pull-bundles/flash-attention/gh-2085`
