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[attention backends] use dedicated wrappers from fa3 for cp.#13165

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sayakpaul wants to merge 2 commits intomainfrom
use-fa3-fwb-bwd-wrappers
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[attention backends] use dedicated wrappers from fa3 for cp.#13165
sayakpaul wants to merge 2 commits intomainfrom
use-fa3-fwb-bwd-wrappers

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@sayakpaul
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What does this PR do?

Great pointer here #12812 (comment) from @vasqu.

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The docs for this PR live here. All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

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LGTM, trusting you that this works as it seems we don't have tests?

Comments are mostly for my interest / nits

repo_id="kernels-community/flash-attn3", function_attr="flash_attn_func", revision="fake-ops-return-probs"
repo_id="kernels-community/flash-attn3",
function_attr="flash_attn_func",
revision="fake-ops-return-probs",
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Ah didnt notice it before, we don't have it merged into main yet?

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We're working on it in #13161.

out,
softmax_lse,
None,
None, # cu_seqlens_q, cu_seqlens_k
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Just fmi, there is no fa varlen cp yet? I think meta had a version at some point

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We handle varlen separately + varlens aren't that common in diffusion use cases.

FLASH_VARLEN_HUB = "flash_varlen_hub"

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trusting you that this works as it seems we don't have tests?

Yes, I manually verified that this works as we're still growing the feature.

@sayakpaul sayakpaul requested a review from DN6 February 19, 2026 14:10
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3 participants