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vllm - 💡(How to fix) Fix [Usage]: GLM-5/GLM-5.1 deployment on L40 with vLLM [1 participants]

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vllm-project/vllm#43172•Fetched 2026-05-20 03:39:35
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Error Message

ValueError: No valid attention backend found for cuda... Reasons: {FLASH_ATTN_MLA: [compute capability not supported], FLASHMLA: [compute capability not supported... only supported on Hopper and Blackwell devices.]}

Fix Action

Fix / Workaround

Is this model fully compatible with L40 currently? If so, are there any known workarounds or specific setup steps for this GPU architecture to fix the kernel issue?

Code Example

ValueError: No valid attention backend found for cuda... Reasons: {FLASH_ATTN_MLA: [compute capability not supported], FLASHMLA: [compute capability not supported... only supported on Hopper and Blackwell devices.]}
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Your current environment

Hi,

I'm trying to evaluate the deployment of GLM-5/GLM-5.1 on an NVIDIA L40 (48GB VRAM). but I'm hitting an "Operator Unsupported" error.

ValueError: No valid attention backend found for cuda... Reasons: {FLASH_ATTN_MLA: [compute capability not supported], FLASHMLA: [compute capability not supported... only supported on Hopper and Blackwell devices.]}

Is this model fully compatible with L40 currently? If so, are there any known workarounds or specific setup steps for this GPU architecture to fix the kernel issue?

How would you like to use vllm

I want to run inference of a [specific model](put link here). I don't know how to integrate it with vllm.

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#environment setup#docker error#permission error#memory optimization#batch processing

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