[Bug]: PLaMo2.1 does not work with v1 engine

[nopperl]

Your current environment

The output of python collect_env.py

Your output of `python collect_env.py` here

🐛 Describe the bug

Running PLaMo2.1 using the recently introduced v1 support fails:

$ VLLM_USE_V1=1 vllm serve pfnet/plamo-2.1-2b-cpt --trust-remote-code --max-model-len 32768 --no-enable-prefix-caching

...
(EngineCore_0 pid=2647201) Process EngineCore_0:
(EngineCore_0 pid=2647201) Traceback (most recent call last):
(EngineCore_0 pid=2647201)   File "/scratch/micromamba/contrib-vllm/lib/python3.12/multiprocessing/process.py", line 314, in _bootstrap
(EngineCore_0 pid=2647201)     self.run()
(EngineCore_0 pid=2647201)   File "/scratch/micromamba/contrib-vllm/lib/python3.12/multiprocessing/process.py", line 108, in run
(EngineCore_0 pid=2647201)     self._target(*self._args, **self._kwargs)
(EngineCore_0 pid=2647201)   File "/scratch/vllm/vllm/v1/engine/core.py", line 716, in run_engine_core
(EngineCore_0 pid=2647201)     raise e
(EngineCore_0 pid=2647201)   File "/scratch/vllm/vllm/v1/engine/core.py", line 703, in run_engine_core
(EngineCore_0 pid=2647201)     engine_core = EngineCoreProc(*args, **kwargs)
(EngineCore_0 pid=2647201)                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
(EngineCore_0 pid=2647201)   File "/scratch/vllm/vllm/v1/engine/core.py", line 504, in __init__
(EngineCore_0 pid=2647201)     super().__init__(vllm_config, executor_class, log_stats,
(EngineCore_0 pid=2647201)   File "/scratch/vllm/vllm/v1/engine/core.py", line 90, in __init__
(EngineCore_0 pid=2647201)     self._initialize_kv_caches(vllm_config)
(EngineCore_0 pid=2647201)   File "/scratch/vllm/vllm/v1/engine/core.py", line 192, in _initialize_kv_caches
(EngineCore_0 pid=2647201)     get_kv_cache_config(vllm_config, kv_cache_spec_one_worker,
(EngineCore_0 pid=2647201)   File "/scratch/vllm/vllm/v1/core/kv_cache_utils.py", line 1119, in get_kv_cache_config
(EngineCore_0 pid=2647201)     raise NotImplementedError
(EngineCore_0 pid=2647201) NotImplementedError

More details: #23998 (comment)

It seems like the MambaSpec.page_size_bytes is half of SlidingWindowSpec.page_size_bytes (not sure why, might be related to the model config). I will have to investigate this further.

Before submitting a new issue...

• Make sure you already searched for relevant issues, and asked the chatbot living at the bottom right corner of the documentation page, which can answer lots of frequently asked questions.