fix local kv_cache_dtype_str

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

@@ -1214,6 +1214,14 @@ class MLACommonImpl(MLAAttentionImpl[M], Generic[M]):
             decode_q = q_ori[:num_decode_tokens]
             prefill_q = q_ori[num_decode_tokens:]
             
+            if self.kv_cache_dtype == "auto":
+                if q.dtype == torch.float16:
+                    kv_cache_dtype_str = "fp16"
+                elif q.dtype == torch.bfloat16:  
+                    kv_cache_dtype_str = "bf16"
+            else:
+                kv_cache_dtype_str = self.kv_cache_dtype
+
         # write the latent and rope to kv cache
         if kv_cache.numel() > 0:
             if not envs.VLLM_USE_LIGHTOP_RMS_ROPE_CONCAT:
@@ -1226,14 +1234,6 @@ class MLACommonImpl(MLAAttentionImpl[M], Generic[M]):
                     scale=layer._k_scale,
                 )
             else:
-                if self.kv_cache_dtype == "auto":
-                    if q.dtype == torch.float16:
-                        kv_cache_dtype_str = "fp16"
-                    elif q.dtype == torch.bfloat16:  
-                        kv_cache_dtype_str = "bf16"
-                else:
-                    kv_cache_dtype_str = self.kv_cache_dtype
-                
                 if torch.cuda.get_device_properties("cuda").gcnArchName.split(':')[0] == "gfx938" and kv_cache_dtype_str=="fp8_e4m3" and envs.VLLM_USE_FUSED_CACHE_QUANT_BMM_MLA:
                     if has_prefill:
                         fused_rms_norm_rope_contiguous(