if kv_cache_detype=="fp8_e4m3", use non fused cat + mla

vllm/v1/attention/backends/mla/flashmla.py

@@ -168,7 +168,7 @@ class FlashMLAImpl(MLACommonImpl[FlashMLAMetadata]):
         assert kv_c_and_k_pe_cache.numel() > 0
         assert attn_metadata.decode is not None
 
-        if not envs.VLLM_USE_CAT_MLA:
+        if not envs.VLLM_USE_CAT_MLA or kv_cache_dtype == "fp8_e4m3":
             if envs.VLLM_USE_OPT_CAT:
                 if q_nope.shape[0] < 1024:
                     from vllm.v1.attention.backends.mla.test_concat import concat_helper_decode
@@ -181,7 +181,7 @@ class FlashMLAImpl(MLACommonImpl[FlashMLAMetadata]):
                 q = torch.cat([q_nope, q_pe], dim=-1)\
                     .unsqueeze(1) # Add seqlen dim of 1 (decode)
 
-        if not envs.VLLM_USE_CAT_MLA:
+        if not envs.VLLM_USE_CAT_MLA or kv_cache_dtype == "fp8_e4m3":
             o, _ = flash_mla_with_kvcache(
                 q=q,
                 k_cache=kv_c_and_k_pe_cache.unsqueeze(-2),  # Add head dim of 1