[Bugfix] Fix MRoPE dispatch on XPU

[yma11]

Purpose

Fix MRoPE dispatch issue on xpu introduced in #24444

Test Plan

VLLM_ALLOW_LONG_MAX_MODEL_LEN=1 VLLM_WORKER_MULTIPROC_METHOD=spawn python3 examples/offline_inference/basic/generate.py --model Qwen/Qwen2.5-VL-7B-Instruct --enforce-eager

Test Result

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• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
• The test plan, such as providing test command.
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[yma11]

@jikunshang please take a review.

[gemini-code-assist]

Code Review

This pull request addresses a dispatch issue for MRoPE (Multimodal Rotary Position Embedding) on XPU devices. The PR description mentions CPU, but the change correctly targets XPU. The MRotaryEmbedding class was incorrectly inheriting the forward_xpu method from its RotaryEmbedding base class. The base implementation lacks support for the specific logic required for multimodal inputs (where positions.ndim == 2), which would lead to incorrect behavior.

The fix introduces a forward_xpu method in the MRotaryEmbedding class that dispatches to its own forward_native implementation. This is the correct approach, as MRotaryEmbedding.forward_native contains the necessary logic to handle multimodal inputs, ensuring correct functionality on XPU devices. This change aligns the XPU implementation with the existing CPU fallback, providing a correct execution path. The change is sound and resolves the bug.

[jikunshang]

what will xpu call without this?

[yma11]

https://github.com/vllm-project/vllm/blob/main/vllm/model_executor/layers/rotary_embedding/base.py#L122, I think this is the expected path but there will be tensor mismatch error when calling the kernel and strange that previously we don't run in this path. I will take a look at this further, but need this fix to unblock Qwen2.5 VL.