GitHub announced free linux/arm64 hosted runners for public repos (GA Aug
2025) under labels `ubuntu-24.04-arm` / `ubuntu-22.04-arm`. Switching the
arm64 leg from QEMU-on-amd64 to a native arm64 matrix runner is ~3x
faster and avoids QEMU's occasional flakiness on long cu128 installs.
The workflow now:
* builds amd64 and arm64 in parallel on their native runners,
pushing each as a single-arch image *by digest* (no tag)
* stitches both digests into one multi-platform manifest in a
follow-up `merge` job, using `docker buildx imagetools create`
* keeps a separate buildx cache scope per platform to avoid
cross-arch cache collisions
Smoke-test job now needs `merge` (was `build`) so it only runs once the
final manifest is published.
Dockerfile header: replace the speculative aarch64 SASS list with the
verified one from pytorch/pytorch v2.10.0 .ci/manywheel/build_cuda.sh
(8.0;9.0;10.0;12.0 on aarch64), and note that sm_120 is forward-compatible
to sm_121 per PyTorch maintainers -- which is what makes DGX Spark work
without an explicit sm_121 SASS section in the wheel.
setup_qemu.sh / test_locally.sh --platform stay in place: they're for
the local-dev path on x86_64 boxes that don't have arm64 hardware.
131f1d3065