Fix test_mamba_ssm_ssd.py due to missing _query_start_loc_to_chunk_indices_offsets

[hl475]

Purpose

#24683 removed the helper function _query_start_loc_to_chunk_indices_offsets and breaks the tests/kernels/mamba/test_mamba_ssm_ssd.py (sample job https://buildkite.com/vllm/ci/builds/32891/steps/canvas?sid=019998c8-1682-4e2d-8161-55a772c16cde) from v1.attention.backends.mamba2_attn as part of the chunk‑aligned Mamba2 changes. This made tests/kernels/mamba/test_mamba_ssm_ssd.py fail at import time. This patch removes the import and computes the small piece of chunk metadata directly in the test, also providing cu_chunk_seqlens and last_chunk_indices expected by the new kernels. No runtime changes.

This PR

Test Plan

pytest tests/kernels/mamba/test_mamba_ssm_ssd.py -v -s

Test Result

======================================================= 348 passed, 1 warning in 823.24s (0:13:43) ========================================================

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[tdoublep]

Does this test not run as part of CI? Didn't realize it was broken.

[tdoublep]

Rather than re-implementing this logic - I think it could be better to refactor the logic into a util function in the meta-data builder and import it (e.g., similarly to how we were doing it for _query_start_loc_to_chunk_indices_offsets).

[hl475]

thanks @tdoublep !

I moved this helper function to vllm/v1/attention/backends/mamba2_attn.py . Let me know what you think!

[hl475]

@tdoublep

Does this test not run as part of CI? Didn't realize it was broken.

Regarding this, from https://github.com/vllm-project/vllm/blob/main/.buildkite/test-pipeline.yaml#L473C10-L480 , my guess is it will run only if changes touch

  source_file_dependencies:
  - csrc/mamba/
  - tests/kernels/mamba

Your PR didn't touch those directories so it didn't get triggered. Let me know if you want to change that, and I am happy to add vllm/v1/attention/backends/mamba2_attn.py into the list!

[mgoin]

Looks reasonable and would like to merge to unblock CI, thank you