[refactor] Refactor the interface for shard weight and remove the flashcomm2 o_shared interface. (#5181)

### What this PR does / why we need it?
- Delete the environment variable
`VLLM_ASCEND_ENABLE_FLASHCOMM2_OSHARED`
- Introduce layer_sharding as a configurable feature in
additional_config
- Revise the term "shared weight" to "shard weight."
Configuration : The feature is opt-in via the additional_config
argument:
```
--additional-config '{
  "layer_sharding": ["o_proj", "q_b_proj"]
}'
```

This is orthogonal to standard tensor parallelism and weight replication
strategies. It is treated as a separate, explicit feature.It can be used
in any scenario, combined with the
flashcomm2https://github.com/vllm-project/vllm-ascend/pull/3232 feature
or the ShardedCP #4702 feature, to achieve significant performance.



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

---------

Signed-off-by: zzhx1 <zzh_201018@outlook.com>
Signed-off-by: zzhxx <zhangzihang23@mails.ucas.ac.cn>
Signed-off-by: chenxiao <Jaychou1620@Gmail.com>
Co-authored-by: clrs97 <524936896@qq.com>
Co-authored-by: Levi-JQ <yujinqi2@huawei.com>
Co-authored-by: chenxiao <Jaychou1620@Gmail.com>

vllm_ascend/utils.py

@@ -23,6 +23,7 @@ import math
 import os
 from contextlib import contextmanager, nullcontext
 from enum import Enum
+from functools import lru_cache
 from threading import Lock
 from typing import TYPE_CHECKING, Any, List, Optional, Tuple, Union
 
@@ -1016,22 +1017,27 @@ def flashcomm2_enable() -> bool:
     return envs_ascend.VLLM_ASCEND_FLASHCOMM2_PARALLEL_SIZE > 0
 
 
-def flashcomm2_o_shared_enabled() -> bool:
-    return envs_ascend.VLLM_ASCEND_ENABLE_FLASHCOMM2_OSHARED
-
-
 def get_flashcomm2_config_and_validate(ascend_config, vllm_config):
     flashcomm2_oproj_tp_size = envs_ascend.VLLM_ASCEND_FLASHCOMM2_PARALLEL_SIZE
     global_tp_size = vllm_config.parallel_config.tensor_parallel_size
-    flashcomm2_oproj_shared = flashcomm2_o_shared_enabled()
 
     if not flashcomm2_enable():
-        flashcomm2_oproj_shared = False
-        return flashcomm2_oproj_tp_size, flashcomm2_oproj_shared
+        return 0
 
     logger.info(
-        f"Enable FLASHCOMM2 with flashcomm2_oproj_tensor_parallel_size = {flashcomm2_oproj_tp_size} and oproj_shared_enabled = {flashcomm2_oproj_shared}"
+        f"Enable FLASHCOMM2 with flashcomm2_oproj_tensor_parallel_size = {flashcomm2_oproj_tp_size}"
     )
+
+    layer_sharding = ascend_config.layer_sharding or []
+    if layer_sharding:
+        if layer_sharding == ["o_proj"]:
+            logger.info_once(
+                "Enable FLASHCOMM2 with o_proj layer sharding for reduced memory consumption."
+            )
+        else:
+            raise ValueError(
+                "FLASHCOMM2 only supports 'o_proj' as the sole layer sharding configuration! "
+                f"Found invalid layer_sharding: {layer_sharding}")
     if not envs_ascend.VLLM_ASCEND_ENABLE_FLASHCOMM1:
         logger.warning_once(
             "It is recommended to enable FLASHCOMM1 simultaneously when starting FLASHCOMM2 for optimal performance."
@@ -1054,13 +1060,10 @@ def get_flashcomm2_config_and_validate(ascend_config, vllm_config):
         )
     if vllm_config.kv_transfer_config is not None and vllm_config.kv_transfer_config.is_kv_consumer:
         raise AssertionError(
-            "FLASHCOMM2 primarily targets P-scenario deployments, "
-            "with additional support for hybrid deployment scenarios. "
-            "It is not applicable in D-scenario environments.")
-    if flashcomm2_oproj_shared:
-        logger.info("Enable FLASHCOMM2 with oproj_shared.")
+            "FLASHCOMM2 primarily targets P-scenario deployments, with additional support for hybrid deployment scenarios. It is not applicable in D-scenario environments."
+        )
 
-    return flashcomm2_oproj_tp_size, flashcomm2_oproj_shared
+    return flashcomm2_oproj_tp_size
 
 
 def get_flashcomm2_reorgnized_batch_ids(global_tp_size) -> list[list[int]]:
@@ -1160,4 +1163,20 @@ def singleton(cls):
             instances[cls] = cls(*args, **kwargs)
         return instances[cls]
 
-    return get_instance
+    return get_instance
+
+
+@lru_cache(maxsize=1)
+def get_current_model_config():
+    from vllm.config import get_current_vllm_config
+    vllm_config = get_current_vllm_config()
+    return vllm_config.model_config
+
+
+#TODO: Temporarily use enable_sp to enable the dsa_cp feature of ds32. and subsequent updates will introduce new interfaces. --zzhx1
+@lru_cache(maxsize=1)
+def enable_dsa_cp() -> bool:
+    from vllm.config import get_current_vllm_config
+    vllm_config = get_current_vllm_config()
+    is_ds_v32 = hasattr(vllm_config.model_config.hf_config, "index_topk")
+    return is_ds_v32 and enable_sp()