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[Bugfix] Disable TRTLLM attention when KV transfer is enabled (#33192)

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Signed-off-by: Zhanqiu Hu <zh338@cornell.edu>
This commit is contained in:
zhanqiuhu
2026-02-04 19:49:18 -05:00
committed by GitHub
parent 4d9513537d
commit bbe0574d8e
1 changed files with 17 additions and 0 deletions
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17
vllm/v1/attention/backends/flashinfer.py
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@@ -573,6 +573,20 @@ class FlashInferMetadataBuilder(AttentionMetadataBuilder[FlashInferMetadata]):
# try to use fp8 q if kv cache is fp8, and will fall back to model dtype
# if TRTLLM attention kernel is not used when building attn metadata
can_use_trtllm = can_use_trtllm_attention(self.num_qo_heads, self.num_kv_heads)
# TRTLLM attention requires strictly contiguous KV cache tensors.
# When KV transfer (P/D disaggregation) is enabled, the KV cache may be
# permuted into non-contiguous views, which causes assertion failures.
self._kv_transfer_enabled = vllm_config.kv_transfer_config is not None
if can_use_trtllm and self._kv_transfer_enabled:
logger.info_once(
"TRTLLM attention is disabled because KV transfer "
"(P/D disaggregation) is enabled. TRTLLM attention requires "
"strictly contiguous KV cache tensors which may not be "
"guaranteed with KV transfer."
)
can_use_trtllm = False
if (
can_use_trtllm
and not vllm_config.attention_config.disable_flashinfer_q_quantization
@@ -822,6 +836,9 @@ class FlashInferMetadataBuilder(AttentionMetadataBuilder[FlashInferMetadata]):
has_sinks=self.has_sinks,
has_spec=uses_spec_reorder,
)
# KV transfer requires non-contiguous KV cache views, incompatible with TRTLLM
if self._kv_transfer_enabled:
prefill_use_trtllm = False
decode_use_trtllm = (
self.use_trtllm_decode_attention and self.dcp_world_size <= 1
)