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[Bugfix] Allocate MLA attention output buffer when None during profiling pass #2

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[Bugfix] Allocate MLA attention output buffer when None during profiling pass #2

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11 changes: 10 additions & 1 deletion vllm/model_executor/layers/attention/mla_attention.py
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Original file line number Diff line number Diff line change
Expand Up @@ -615,7 +615,16 @@ def forward_impl(
quant_col_major: bool | None = None,
quant_tma_aligned: bool | None = None,
) -> torch.Tensor:
assert output is not None, "Output tensor must be provided."
# [Bugfix] vLLM profiling run (_dummy_run) calls forward_impl
# without an output buffer — it only needs shape info, not values.
# The assertion is too strict for this case. Allocate a zero buffer
# when output is None. During real inference, callers always provide
# a buffer so this path is never taken outside of startup profiling.
if output is None:
output = torch.zeros(
(q.shape[0], self.num_heads, self.v_head_dim),
dtype=q.dtype,
device=q.device,)

quant_key = _detect_output_quant_key(
output, output_scale, output_block_scale, self.num_heads * self.v_head_dim
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