Only build CUTLASS MoE kernels on Hopper

[huydhn]

Purpose

Fix #18841 and unblock 0.9.2 release

10.0 was added by #16362, but the kernels only work on 9.0 Hopper

Test Plan

Rebuild vLLM locally and load meta-llama/Llama-4-Maverick-17B-128E-Instruct-FP8 on a 8xH100 server

from vllm import LLM

LLM(
    model="meta-llama/Llama-4-Maverick-17B-128E-Instruct-FP8",
    tensor_parallel_size=8,
    max_model_len=8192,
)

Test Result

The model is loaded successfully instead of failing with CUDA error: no kernel image is available for execution on the device

cc @simon-mo @houseroad

[github-actions]

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[gemini-code-assist]

Summary of Changes

Hello @huydhn, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a build and runtime issue where CUTLASS MoE kernels, which are only compatible with Hopper architecture, were being compiled for other architectures like Ada Lovelace (sm_100a). By modifying the CMake build configuration to target only Hopper, this change prevents compilation errors and ensures that users on non-Hopper GPUs do not encounter runtime errors related to missing kernels, specifically fixing issue #18841 and unblocking the 0.9.2 release.

Highlights

• Build Configuration: Restricted the CUDA architectures targeted for building CUTLASS MoE kernels to only include Hopper (sm_90a).

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[gemini-code-assist]

Code Review

This pull request addresses a build issue where CUTLASS MoE kernels, designed exclusively for Hopper (9.0a) architecture, were incorrectly being considered for compilation on newer, incompatible architectures (e.g., 10.0a). This previously led to runtime errors due to missing kernel images for the target device.

The fix involves a targeted change in CMakeLists.txt that modifies the cuda_archs_loose_intersection call. It now correctly specifies only "9.0a" as a source architecture for these MoE kernels, preventing their erroneous build for other architectures. A minor update to a comment also helps to emphasize this Hopper-only restriction.

The changes are clear, directly resolve the described issue, and the provided test plan and results confirm the fix. The code modification aligns with the intended behavior and existing documentation within the comments.

[LucasWilkinson]

Nice good catch! Thank you! (Will have to investigate why the cmake didn't build 9.0a at all but this is a good fix regardless)

[houseroad]

Looks good, thanks!