cmake: add VLLM_XPU_LIBS_ONLY + prebuilt-kernel-lib hooks#345
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jasonboukheir wants to merge 2 commits into
Draft
cmake: add VLLM_XPU_LIBS_ONLY + prebuilt-kernel-lib hooks#345jasonboukheir wants to merge 2 commits into
jasonboukheir wants to merge 2 commits into
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Adds two CMake-level affordances for build systems that produce the
per-target kernel .so files outside the upstream cmake build
(distributed CI, sccache shards, Bazel, Buck2, Nix per-derivation
builds):
* VLLM_XPU_LIBS_ONLY (OFF by default): when ON, the build configures
and emits the kernel-library targets (attn_kernels_xe_2, ...) but
skips the host-side Python extension modules. Use case: build just
the .so artifacts for caching / sharing between consumers.
* VLLM_XPU_PREBUILT_<NAME>_LIB: a per-library override that wires an
existing .so in as a SHARED IMPORTED target instead of building it
from source. The downstream extension module then links against the
imported target by name. Use case: assemble the final wheel from a
mix of cached / locally-rebuilt kernel libs.
* setup.py forwards VLLM_XPU_PREBUILT_*_LIB env vars through to
cmake-configure so the same overrides work via pip install.
All defaults are no-ops on existing upstream builds: when no option is
set and no _LIB env var is exported, the build is byte-equivalent to
the unpatched tree.
…*_LIB
Libs supplied via the prebuilt-lib hook (added in the parent commit) are
wired in as SHARED IMPORTED targets in CMakeLists.txt and the
corresponding csrc/.../{lib} subdir is intentionally never
add_subdirectory()'d. The build/temp dir for that subdir therefore
doesn't exist, and `cmake --install --component <lib>` fails when it
tries to chdir there.
Skip the install step when the matching VLLM_XPU_PREBUILT_<NAME>_LIB env
var is set — the .so is already in its final location, no install needed.
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Adds two CMake-level affordances for build systems that produce the per-target kernel
.sofiles outside the upstream cmake build (distributed CI, sccache shards, Bazel, Buck2, Nix per-derivation builds).Changes
Commit 1 —
cmake: add VLLM_XPU_LIBS_ONLY + prebuilt-kernel-lib hooksVLLM_XPU_LIBS_ONLY(OFF by default): when ON, the build configures and emits the kernel-library targets (attn_kernels_xe_2, ...) but skips the host-side Python extension modules. Use case: build just the.soartifacts for caching / sharing between consumers.VLLM_XPU_PREBUILT_<NAME>_LIB: a per-library override that wires an existing.soin as aSHARED IMPORTEDtarget instead of building it from source. The downstream extension module then links against the imported target by name. Use case: assemble the final wheel from a mix of cached / locally-rebuilt kernel libs.setup.pyforwardsVLLM_XPU_PREBUILT_*_LIBenv vars through to cmake-configure so the same overrides work viapip install.Commit 2 —
setup.py: skip cmake-install for libs supplied via VLLM_XPU_PREBUILT_*_LIBLibs supplied via the prebuilt-lib hook are wired in as
SHARED IMPORTEDtargets and the correspondingcsrc/.../{lib}subdir is intentionally neveradd_subdirectory()'d, so its build/temp dir doesn't exist forcmake --installto chdir into. Skip the install step in that case — the.sois already in its final location.Backwards compatibility
All defaults are no-ops on existing upstream builds: when no option is set and no
_LIBenv var is exported, the build is byte-equivalent to the unpatched tree.Motivation
This is the minimum surface needed for a Nix per-derivation build that compiles each kernel library independently and assembles them into the final wheel. The same mechanism is useful for any consumer that wants to cache kernel-lib
.soartifacts across builds.Draft — happy to iterate on naming / option style.