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[Bugfix][CUDA] fixes CUDA FP8 kv cache dtype supported #21420

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Merged
vllm-bot merged 1 commit into from
Jul 23, 2025
Merged

[Bugfix][CUDA] fixes CUDA FP8 kv cache dtype supported #21420

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26 changes: 13 additions & 13 deletions vllm/platforms/cuda.py
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Original file line number Diff line number Diff line change
Expand Up @@ -456,6 +456,19 @@ def stateless_init_device_torch_dist_pg(
def device_count(cls) -> int:
return cuda_device_count_stateless()

@classmethod
def is_kv_cache_dtype_supported(cls, kv_cache_dtype: str) -> bool:
fp8_attention = kv_cache_dtype.startswith("fp8")
will_use_fa = (not envs.is_set("VLLM_ATTENTION_BACKEND")
) or envs.VLLM_ATTENTION_BACKEND == "FLASH_ATTN_VLLM_V1"
supported = False
if cls.is_device_capability(100):
supported = True
elif fp8_attention and will_use_fa:
from vllm.attention.utils.fa_utils import flash_attn_supports_fp8
supported = flash_attn_supports_fp8()
return supported


# NVML utils
# Note that NVML is not affected by `CUDA_VISIBLE_DEVICES`,
Expand Down Expand Up @@ -583,19 +596,6 @@ def is_fully_connected(cls, physical_device_ids: list[int]) -> bool:
" not found. Assuming no NVLink available.")
return False

@classmethod
def is_kv_cache_dtype_supported(cls, kv_cache_dtype: str) -> bool:
fp8_attention = kv_cache_dtype.startswith("fp8")
will_use_fa = (not envs.is_set("VLLM_ATTENTION_BACKEND")
) or envs.VLLM_ATTENTION_BACKEND == "FLASH_ATTN_VLLM_V1"
supported = False
if cls.is_device_capability(100):
supported = True
elif fp8_attention and will_use_fa:
from vllm.attention.utils.fa_utils import flash_attn_supports_fp8
supported = flash_attn_supports_fp8()
return supported


# Autodetect either NVML-enabled or non-NVML platform
# based on whether NVML is available.
Expand Down