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[build] do not compile FA3 for < sm_90 #105

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Merged
LucasWilkinson merged 7 commits into from
Nov 17, 2025
+4 −13
Merged

[build] do not compile FA3 for < sm_90 #105

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8f25773
[build] do not compile FA3 for < sm_90
AlpinDale Nov 6, 2025
3e16ec5
exclude FA3 for anything not hopper in the python side
AlpinDale Nov 6, 2025
62f3909
exclude blackwell as well
AlpinDale Nov 6, 2025
3d9959a
additional checks
AlpinDale Nov 6, 2025
184eee2
Revert "additional checks"
AlpinDale Nov 6, 2025
fcb36f7
Revert "exclude blackwell as well"
AlpinDale Nov 6, 2025
60a201a
Merge branch 'main' into no-ampere-fa3
LucasWilkinson Nov 17, 2025
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8 changes: 1 addition & 7 deletions CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -191,9 +191,6 @@ if (FA3_ENABLED AND ${CMAKE_CUDA_COMPILER_VERSION} GREATER_EQUAL 12.0)
"hopper/instantiations/flash_fwd_hdim64_512_bf16*_sm90.cu"
"hopper/instantiations/flash_fwd_hdim192_128_bf16*_sm90.cu")
list(APPEND FA3_BF16_GEN_SRCS ${FA3_BF16_GEN_SRCS_})
file(GLOB FA3_BF16_GEN_SRCS_
"hopper/instantiations/flash_fwd_*_bf16_*_sm80.cu")
list(APPEND FA3_BF16_GEN_SRCS ${FA3_BF16_GEN_SRCS_})

# FP16 source files
file(GLOB FA3_FP16_GEN_SRCS
Expand All @@ -208,9 +205,6 @@ if (FA3_ENABLED AND ${CMAKE_CUDA_COMPILER_VERSION} GREATER_EQUAL 12.0)
"hopper/instantiations/flash_fwd_hdim64_512_fp16*_sm90.cu"
"hopper/instantiations/flash_fwd_hdim192_128_fp16*_sm90.cu")
list(APPEND FA3_FP16_GEN_SRCS ${FA3_FP16_GEN_SRCS_})
file(GLOB FA3_FP16_GEN_SRCS_
"hopper/instantiations/flash_fwd_*_fp16_*_sm80.cu")
list(APPEND FA3_FP16_GEN_SRCS ${FA3_FP16_GEN_SRCS_})

# FP8 source files
file(GLOB FA3_FP8_GEN_SRCS
Expand All @@ -229,7 +223,7 @@ if (FA3_ENABLED AND ${CMAKE_CUDA_COMPILER_VERSION} GREATER_EQUAL 12.0)
# For CUDA we set the architectures on a per file basis
# FaV3 is not yet supported in Blackwell
if (VLLM_GPU_LANG STREQUAL "CUDA")
cuda_archs_loose_intersection(FA3_ARCHS "8.0;9.0a;" "${CUDA_ARCHS}")
cuda_archs_loose_intersection(FA3_ARCHS "9.0a;" "${CUDA_ARCHS}")
message(STATUS "FA3_ARCHS: ${FA3_ARCHS}")

set_gencode_flags_for_srcs(
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9 changes: 3 additions & 6 deletions vllm_flash_attn/flash_attn_interface.py
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Original file line number Diff line number Diff line change
Expand Up @@ -48,13 +48,10 @@ def _is_fa2_supported(device = None) -> Tuple[bool, Optional[str]]:
def _is_fa3_supported(device = None) -> Tuple[bool, Optional[str]]:
if not FA3_AVAILABLE:
return False, f"FA3 is unavaible due to: {FA3_UNAVAILABLE_REASON}"
if torch.cuda.get_device_capability(device)[0] < 8 \
or torch.cuda.get_device_capability(device)[0] >= 10 \
or torch.cuda.get_device_capability(device) == (8, 6) \
or torch.cuda.get_device_capability(device) == (8, 9):
if torch.cuda.get_device_capability(device)[0] < 9 \
or torch.cuda.get_device_capability(device)[0] >= 10:
return False, \
"FA3 is only supported on devices with compute capability >= 8" \
" excluding 8.6 and 8.9 and Blackwell archs (>=10)"
"FA3 is only supported on devices with compute capability 9.0"
return True, None

def _is_fa4_supported(device = None) -> Tuple[bool, Optional[str]]:
Expand Down