[P/D] check kv extra config and del hccl backend (#4547)

### What this PR does / why we need it?
check kv extra config & del hccl backend


- vLLM version: v0.12.0
- vLLM main:
ad32e3e19c

---------

Signed-off-by: liziyu <liziyu16@huawei.com>
Co-authored-by: wangxiyuan <wangxiyuan1007@gmail.com>

vllm_ascend/ascend_config.py

@@ -28,6 +28,37 @@ def _check_torchair_supported(model_type: str):
     return False
 
 
+def check_kv_extra_config(vllm_config):
+
+    def _check(name: str, config: dict):
+        tp_key = "tp_size"
+        dp_key = "dp_size"
+        if tp_key in config:
+            config_tp = config[tp_key]
+            vllm_tp = vllm_config.parallel_config.tensor_parallel_size
+            if config_tp != vllm_tp:
+                raise ValueError(
+                    f"KV transfer '{name}' config has a conflicting tensor parallel size. "
+                    f"Expected {vllm_tp}, but got {config_tp}.")
+        if dp_key in config:
+            config_dp = config[dp_key]
+            vllm_dp = vllm_config.parallel_config.data_parallel_size
+            if config_dp != vllm_dp:
+                raise ValueError(
+                    f"KV transfer '{name}' config has a conflicting data parallel size. "
+                    f"Expected {vllm_dp}, but got {config_dp}.")
+
+    if vllm_config.kv_transfer_config.is_kv_producer:
+        _check(
+            "prefill",
+            vllm_config.kv_transfer_config.get_from_extra_config(
+                "prefill", {}))
+    if vllm_config.kv_transfer_config.is_kv_consumer:
+        _check(
+            "decode",
+            vllm_config.kv_transfer_config.get_from_extra_config("decode", {}))
+
+
 class AscendConfig:
     """
     Configuration Object for additional_config from vllm.configs.
@@ -112,6 +143,10 @@ class AscendConfig:
                 )
         self.enable_cpu_binding = additional_config.get(
             "enable_cpu_binding", False)
+
+        if vllm_config.kv_transfer_config is not None:
+            check_kv_extra_config(vllm_config)
+
         self.pd_tp_ratio = 1
         self.pd_head_ratio = 1
         self.num_head_replica = 1