Add support for multi-arch and multi-platform cuda toolchains by charleysaintNV · Pull Request #422 · bazel-contrib/rules_cuda

charleysaintNV · 2025-12-04T19:59:33Z

This MR adds support for multiple architectures and multiple versions of a toolchain. Using the redis_json you can create multiple versions of a toolchain:

cuda.redist_json(
    name = "cuda_13_0_2",
    version = "13.0.2",
    platforms = [
        "linux-x86_64",
        "linux-sbsa",
    ],
)
cuda.redist_json(
    name = "cuda_13_0_0",
    version = "13.0.0",
    platforms = [
        "linux-x86_64",
        "linux-sbsa",
    ],
)
cuda.redist_json(
    name = "cuda_12_8_0",
    version = "12.8.0",
    platforms = [
        "linux-x86_64",
        "linux-sbsa",
    ],
)

cuda.toolkit(name = "cuda")
use_repo(cuda,"cuda")

then using a set of flags in .bazelrc you can control which version of the toolchain to use in a given config:

build --@rules_cuda//cuda:exec_platform="linux-x86_64"
build --@rules_cuda//cuda:target_platform="linux-x86_64"
build --@rules_cuda//cuda:version="13.0.0"

…-arch' Enable multi-version builds See merge request csaint/rules_cuda!1

cuda/BUILD.bazel

cuda/private/repositories.bzl

steple

Thanks for adding this, I think this will be very useful.

cuda/BUILD.bazel

charleysaintNV · 2025-12-05T04:18:03Z

pushed a new commit with the versions stuff moved around and all in one place at least and I changed the name of the nvcc_platform and runtime_platform to exec and target

cuda/dummy/BUILD.bazel

cuda/private/templates/BUILD.cufile

cloudhan · 2025-12-07T16:16:53Z

cuda/extensions.bzl

+        "linux_x86_64_repo": attr.string(
+            mandatory = True,
+            doc = "Name of the repository to use for x86_64 platform",
+        ),
+        "linux_aarch64_repo": attr.string(
+            mandatory = True,
+            doc = "Name of the repository to use for ARM64/Jetpack platform",
+        ),
+        "linux_sbsa_repo": attr.string(
+            mandatory = True,
+            doc = "Name of the repository to use for SBSA platform",
+        ),


would a platform_mapping with attr.string_dict be better here? Validating the key in the rule impl seem to be future proof.

cloudhan · 2025-12-07T16:23:13Z

cuda/extensions.bzl

    for _, toolkit in registrations.items():
        if components_mapping != None:
-            cuda_toolkit(name = toolkit.name, components_mapping = components_mapping, version = redist_version)
+            # Always use the maximum version so the toolkit includes all components.


This is not quite true if CTK delete some component in the future. I think a union across all CTK versions will be a little bit more robust.

This could take some work, right now the version in cuda_toolkit isn't going to necessarily be correct since it's pointing to @cuda which can point to any number of versioned cuda repos, but I don't know if that gets used anywhere in the rules so I'll try removing it and see what falls out...

The logic is pretty deeply embedded in the repository rules where I can't use the value of a flag. I might need to go back and add the ability to register multiple toolkits to get everything to work as expected...

Lets leave it for future improvement, just point it out :)

cuda/private/templates/BUILD.cufile

cuda/dummy/libdevice.10.bc

When a CUDA component (like cuda_crt) doesn't exist for a platform (like linux-aarch64), builds would fail because the select() had no matching condition for that platform. Now platform aliases are generated for ALL platforms, with dummy targets used for platforms where the component doesn't exist. This ensures builds on any platform have matching select conditions. Also consolidates platform definitions into a single source of truth in cuda/private/platforms.bzl and removes unused backward-compatibility code. Fixes JP6 (linux-aarch64, CUDA 12) build failure where cuda_crt (a CUDA 13+ only component) caused select() to fail.

lgulich · 2026-01-27T14:33:46Z

Hey @cloudhan , I pushed a new commit addressing your comments.

I also added some additional changes:

Added more dummy fallbacks for some targets that don't exist on aarch64/cuda12 (e.g. culibos)
Created cuda/private/platforms.bzl as single source of truth for
supported platforms

cloudhan · 2026-01-28T14:00:45Z

Good, we should have some tests against this new feature. I'd like to do it myself and make a PR to your branch before I can proceed.

lgulich · 2026-01-29T18:32:19Z

Sure, I've asked @charleysaintNV to give you access to the repo to push to the branch

lgulich · 2026-02-02T21:43:56Z

Sure, I've asked @charleysaintNV to give you access to the repo to push to the branch

You should now have access

charleysaintNV and others added 5 commits December 4, 2025 01:26

add multi-platform and multi-version support to rules_cuda

6f3d716

fix alias targets that have a path

235a94a

Enable multi-version builds

d6a7478

Merge branch 'lgulich/enable-multi-version-builds' into 'csaint/multi…

5e605df

…-arch' Enable multi-version builds See merge request csaint/rules_cuda!1

add error messages for bad platform/version selection

7bc9c61

charleysaintNV requested review from cloudhan, jsharpe and ryanleary as code owners December 4, 2025 19:59

cloudhan reviewed Dec 5, 2025

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cloudhan reviewed Dec 5, 2025

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steple reviewed Dec 5, 2025

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move versions and chaange flag names

3e1f206

charleysaintNV added 2 commits December 5, 2025 04:18

remove todos

53f739e

remove list of versions

4233145

charleysaintNV requested review from cloudhan and steple December 5, 2025 19:09

cloudhan reviewed Dec 7, 2025

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fix issues with dummy files

9fbd1ab

cloudhan reviewed Dec 9, 2025

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lgulich added 2 commits January 15, 2026 19:38

Fix typos

d9cfe1c

lgulich force-pushed the csaint/multi-arch branch from db0a73a to 7eb64fe Compare January 27, 2026 14:24

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charleysaintNV commented Dec 4, 2025 •

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