Make the docker image multi-arch so DGX Spark (GB10, sm_121, aarch64) and
the Grace-Hopper / Grace-Blackwell SoCs (GH200 arm64, GB200 arm64) pull a
natively-built arm64 child from the same manifest. Runtime emulation is
NOT involved -- QEMU is used only for the cross-compile step on x86_64
CI runners; consumers on aarch64 hosts get a normal arm64 image and CUDA
works as on any other host.
Dockerfile:
* ARG TARGETARCH; switch unsloth extras between cu128-ampere-torch2100
(amd64, with xformers) and huggingface (arm64, no xformers -- there
is no cu128 aarch64 xformers wheel as of 0.0.34, so we fall back to
Unsloth's native SDPA path; ~5-10% slowdown but functionally complete).
* Build-time torch._C._cuda_getArchFlags() assertion: amd64 still
requires sm_120, arm64 accepts sm_120 or sm_121.
* Same TORCH_CUDA_ARCH_LIST on both arches; nvcc emits whatever's listed.
docker/setup_qemu.sh (new):
One-time host setup -- registers binfmt_misc handlers via
tonistiigi/binfmt and creates a 'unsloth-multiarch' docker-container
buildx builder. Required only on x86_64 build hosts targeting arm64.
docker/test_locally.sh:
--platform amd64|arm64 flag. Cross-builds verify QEMU is registered,
then build through the in-image arch-flags assertion. Smoke + notebook
blocks auto-skip when image arch != host arch (CUDA cannot run under
user-space QEMU + nvidia-container-toolkit cannot bridge a QEMU guest
to a real GPU).
.github/workflows/docker-publish.yml:
platforms: linux/amd64,linux/arm64 (single manifest, two children).
Timeout bumped 60 -> 150 min for the slower arm64-under-QEMU leg.
docker/setup-qemu-action@v3 with platforms: arm64 (was implicit before).
e7cfceadab