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fix image selection, WSL2 detection and gpu device passthrough - #2936

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Follow-up to PR #2932 to resolve issue found while working on NVIDIA Vulkan.

Fixes image selection in --backend=auto mode when GPU environment variables are set.
Fixes GPU detection logic when running within the Windows WSL2 VM.
Stop passing through iGPUs by default when an NVIDIA is detected.

Image selection keys off the resolved backend's GPU environment variable,
which in auto mode is not the one the hardware was detected as. Two things
fall out of that for a GPU that resolves to the vulkan backend:

An image the user configured for their GPU, e.g. images.HIP_VISIBLE_DEVICES,
is never looked up, because the lookup happens after the key has been
rewritten to GGML_VK_VISIBLE_DEVICES. Consult the detected GPU first in auto
mode, so a pin for the hardware wins over one for the resolved backend.

default_image / RAMALAMA_DEFAULT_IMAGE is ignored, because the vulkan entry
in the image table hardcodes the published quay.io/ramalama/ramalama tag.
With no GPU at all the same code path returns default_image, so the two
disagreed. Drop the entry and let it fall through.

Signed-off-by: Oliver Walsh <owalsh@redhat.com>
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📝 Summary

Summary by CodeRabbit

  • New Features

    • Improved GPU device selection to honor accelerator visibility settings and selected NVIDIA GPUs.
    • Added broader WSL2 support for AMD ROCm and Intel SYCL GPU backends.
    • NVIDIA containers now receive only selected GPUs, with container GPU numbering remapped automatically.
    • Improved automatic backend and container image selection on Windows and WSL2.
    • Host accelerator devices are no longer added to NVIDIA-only containers by default.
  • Documentation

    • Clarified WSL2 backend recommendations, Vulkan availability, and GPU visibility behavior.
    • Documented how to explicitly re-add excluded devices when needed.

Walkthrough

The change adds WSL2 detection, applies accelerator environment variables to GPU device discovery, updates backend and image selection, adjusts container device mappings, and revises related documentation and tests.

Changes

WSL2 GPU backend and device handling

Layer / File(s) Summary
WSL2 backend detection and image selection
ramalama/common.py, ramalama/plugins/runtimes/inference/llama_cpp.py, test/unit/test_common.py, test/unit/test_inference_engine_plugins.py, test/unit/conftest.py
Adds cached WSL2 detection and uses it for backend preference. Vulkan now uses the configured default image. Automatic image selection checks configured GPU and backend images.
Accelerator-aware device wiring
ramalama/engine.py, ramalama/compose.py, ramalama/kube.py, ramalama/quadlet.py, test/unit/test_engine.py, test/unit/test_quadlet.py, test/unit/data/test_compose/*, test/unit/data/test_quadlet/*
GPU discovery uses accelerator environment variables. CUDA returns no host GPU device map. WSL adds /dev/dxg and /usr/lib/wsl. Quadlet and fixture device mappings separate NVIDIA allocation from host accelerator devices.
Backend and GPU device documentation
docs/options/backend.md, docs/ramalama-*.md, docs/ramalama.conf*
Backend notes use WSL2 for AMD and Intel vendor backends. CUDA documentation explains selected GPU passthrough and manual /dev/dri access.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~30 minutes

Change: Bug fix

Sequence Diagram(s)

sequenceDiagram
  participant Runtime
  participant common
  participant Container
  Runtime->>common: read accelerator environment variables
  common-->>Runtime: selected GPU device paths
  Runtime->>Container: add backend-specific devices and mounts
Loading

Merge Risk: 🔵 Low · up to 4dee9

The runtime changes are mergeable, but users may receive misleading guidance about selected GPU visibility and Vulkan support on WSL2.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name Status Explanation Resolution
Docstring Coverage ⚠️ Warning Docstring coverage is 26.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 50 functions across 11 files. Write docstrings for the functions missing them to satisfy the coverage threshold.
✅ Passed checks (4 passed)
Check name Status Explanation
Title check ✅ Passed The title clearly summarizes the main changes: image selection, WSL2 detection, and GPU device passthrough.
Description check ✅ Passed The description directly explains the changes to image selection, WSL2 GPU detection, and integrated GPU passthrough.
Linked Issues check ✅ Passed Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check ✅ Passed Check skipped because no linked issues were found for this pull request.
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Actionable comments posted: 5

🧹 Nitpick comments (1)
test/unit/conftest.py (1)

49-49: 📐 Maintainability & Code Quality | 🔵 Trivial | ⚡ Quick win

Add type hints to the changed test code.

The repository guideline applies to all Python files, including tests. Add the generator return annotation to _clear_wsl_cache, annotate not_windows_or_wsl parameters and return value, and annotate the changed test functions, helper parameters and return values, and devices in test/unit/test_common.py.

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In `@test/unit/conftest.py` at line 49, Update the changed Python test code with
complete type hints: annotate _clear_wsl_cache’s generator return type,
not_windows_or_wsl’s parameters and return value, all changed test functions and
helpers with parameter and return types, and the devices variable in
test_common.py, using the repository’s existing typing conventions.

  • 🪄 Fix CodeRabbit comments on this PR
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Inline comments:
In `@docs/ramalama-cuda.7.md`:
- Around line 141-142: Update the GPU passthrough description near the NVIDIA
container toolkit guidance to qualify that matching CDI entries pass only the
selected GPUs, while an unavailable or incomplete CDI configuration falls back
to passing all detected GPUs. Keep the existing explanation about explicitly
adding /dev/dri for other host devices.

In `@docs/ramalama-run.1.md`:
- Around line 69-71: Update the WSL2 backend guidance in the documentation
copies around the Vulkan note: state that vendor-specific backends such as rocm
and sycl are preferred, while Vulkan remains supported as a fallback and can be
explicitly selected with --backend=vulkan. Apply the same wording consistently
to all five copies.

In `@ramalama/engine.py`:
- Around line 153-160: Update add_device_options() so the WSL2 resource
attachment for /dev/dxg and /usr/lib/wsl is shared by both HIP_VISIBLE_DEVICES
and INTEL_VISIBLE_DEVICES, while retaining the wsl_devices_added guard. Add a
test covering HIP_VISIBLE_DEVICES on WSL2 and verifying both attachments are
applied.

In `@ramalama/quadlet.py`:
- Around line 71-75: Update Quadlet.generate() to read the live
nvidia_selected_devices value from ramalama.common and emit one Container
AddDevice entry using nvidia.com/gpu=<name> for each selected CDI device. Emit
nvidia.com/gpu=all only when the selection is empty, preserving the existing
CUDA-only behavior.

In `@test/unit/test_engine.py`:
- Line 61: Update the new test helpers and test methods in the affected test
class with type hints: annotate accel_env_vars and windows_or_wsl, add explicit
return annotations to each helper, and use -> None for every new test method.
Keep the existing behavior unchanged and ensure the annotations are compatible
with mypy.

---

Nitpick comments:
In `@test/unit/conftest.py`:
- Line 49: Update the changed Python test code with complete type hints:
annotate _clear_wsl_cache’s generator return type, not_windows_or_wsl’s
parameters and return value, all changed test functions and helpers with
parameter and return types, and the devices variable in test_common.py, using
the repository’s existing typing conventions.

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  • docs/options/backend.md
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  • docs/ramalama-sandbox-goose.1.md
  • docs/ramalama-sandbox-opencode.1.md
  • docs/ramalama-sandbox-pi.1.md
  • docs/ramalama-serve.1.md
  • docs/ramalama.conf
  • docs/ramalama.conf.5.md
  • ramalama/common.py
  • ramalama/compose.py
  • ramalama/engine.py
  • ramalama/kube.py
  • ramalama/plugins/runtimes/inference/llama_cpp.py
  • ramalama/quadlet.py
  • test/unit/conftest.py
  • test/unit/data/test_compose/with_nvidia_gpu.yaml
  • test/unit/data/test_compose/with_nvidia_gpu_selection.yaml
  • test/unit/data/test_compose/with_nvidia_gpu_vulkan_image.yaml
  • test/unit/data/test_quadlet/basic/tinyllama.container
  • test/unit/data/test_quadlet/draft_model/tinyllama.container
  • test/unit/data/test_quadlet/empty/tinyllama.container
  • test/unit/data/test_quadlet/modelfromstore/modelfromstore.container
  • test/unit/data/test_quadlet/modelfromstore_add_to_unit/modelfromstore_add_to_unit.container
  • test/unit/data/test_quadlet/modelfromstore_ct/modelfromstore_ct.container
  • test/unit/data/test_quadlet/modelfromstore_mmproj/modelfromstore_mmproj.container
  • test/unit/data/test_quadlet/multipart/gpt-oss-120b.container
  • test/unit/data/test_quadlet/oci_basic/oci-model.container
  • test/unit/data/test_quadlet/oci_port/oci-model-port.container
  • test/unit/data/test_quadlet/oci_rag/oci-model-rag.container
  • test/unit/data/test_quadlet/portmapping/tinyllama.container
  • test/unit/test_common.py
  • test/unit/test_engine.py
  • test/unit/test_inference_engine_plugins.py
💤 Files with no reviewable changes (15)
  • test/unit/data/test_compose/with_nvidia_gpu.yaml
  • test/unit/data/test_quadlet/modelfromstore/modelfromstore.container
  • test/unit/data/test_compose/with_nvidia_gpu_vulkan_image.yaml
  • test/unit/data/test_quadlet/modelfromstore_ct/modelfromstore_ct.container
  • test/unit/data/test_quadlet/modelfromstore_add_to_unit/modelfromstore_add_to_unit.container
  • test/unit/data/test_quadlet/draft_model/tinyllama.container
  • test/unit/data/test_compose/with_nvidia_gpu_selection.yaml
  • test/unit/data/test_quadlet/oci_rag/oci-model-rag.container
  • test/unit/data/test_quadlet/portmapping/tinyllama.container
  • test/unit/data/test_quadlet/multipart/gpt-oss-120b.container
  • test/unit/data/test_quadlet/basic/tinyllama.container
  • test/unit/data/test_quadlet/oci_basic/oci-model.container
  • test/unit/data/test_quadlet/oci_port/oci-model-port.container
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Comment thread docs/ramalama-cuda.7.md Outdated
Comment thread docs/ramalama-run.1.md Outdated
Comment thread ramalama/engine.py Outdated
Comment thread ramalama/quadlet.py Outdated
Comment thread test/unit/test_engine.py
Backend preferences already avoided Vulkan on Windows, because WSL2 exposes
GPUs through /dev/dxg and Vulkan there means mesa's dzn driver translating
to D3D12 (no cooperative matrix support, no compute tuning) or a silent
llvmpipe fallback.

That check used platform.system() == "Windows", which is only true for a
native Windows interpreter. Running ramalama inside the WSL2 distro itself
reports "Linux" and got the Linux defaults. Add is_windows_or_wsl()
alongside the other platform predicates in common, covering both cases, and
use it for the AMD and Intel preference overrides.

The /dev/dxg passthrough and /usr/lib/wsl bind mount in add_device_options()
move to the same predicate. They are needed wherever the GPU comes in
through WSL, so leaving them on the Windows check would have picked the
sycl image inside a distro and then handed it no GPU at all.

Describe the split in the docs as WSL2 rather than Windows to match, and
reflow the dangling comment in the sample config while touching it.

in_wsl() caches its /proc read, so clear it around every test in conftest,
as in_toolbox already does.

Signed-off-by: Oliver Walsh <owalsh@redhat.com>
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olliewalsh force-pushed the vulkan-on-nvidia-fixes branch from 8935733 to eff73cc Compare September 18, 2026 12:40
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Actionable comments posted: 2


  • 🪄 Fix CodeRabbit comments on this PR
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Inline comments:
In `@test/unit/test_engine.py`:
- Line 65: Update the native HIP test helper’s patch context to mock
ramalama.engine.is_windows_or_wsl as False alongside get_accel_env_vars,
ensuring _host_gpu_device_args() uses native device mappings without
WSL-specific entries.

In `@test/unit/test_quadlet.py`:
- Line 330: Update test_quadlet_nvidia_selection and the related Quadlet
construction to add the appropriate monkeypatch and return type annotations, and
pass a boolean False for artifact instead of an empty string so the test remains
compatible with Quadlet.__init__ and mypy.

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Comment thread test/unit/test_engine.py
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Caution

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⚠️ Outside diff range comments (1)

🟠 Major · Remap CUDA_VISIBLE_DEVICES in Quadlet output. · quadlet.py:139-145

ramalama/quadlet.py:139-145
🎯 Functional Correctness | 🟠 Major | ⚡ Quick win

Remap CUDA_VISIBLE_DEVICES in Quadlet output.

When nvidia_selected_devices contains host indices such as ["1"], Quadlet adds only nvidia.com/gpu=1 but _gen_env() writes CUDA_VISIBLE_DEVICES=1 unchanged. The container renumbers its single exposed GPU as 0, so CUDA can hide the allocated GPU. Compose and Engine already use container_cuda_visible_devices() for this remapping.

Apply the same conversion in Quadlet:

Proposed fix
-from ramalama.common import MNT_DIR, RAG_DIR, ContainerEntryPoint, get_accel, get_accel_env_vars
+from ramalama.common import (
+    MNT_DIR,
+    RAG_DIR,
+    ContainerEntryPoint,
+    container_cuda_visible_devices,
+    get_accel,
+    get_accel_env_vars,
+)
...
         env_var_string = ""
         for k, v in get_accel_env_vars().items():
+            if k == "CUDA_VISIBLE_DEVICES":
+                v = container_cuda_visible_devices(v)
             quadlet_file.add("Container", "Environment", f"{k}={v}")
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In `@ramalama/quadlet.py` around lines 139 - 145, Update _gen_env to remap
CUDA_VISIBLE_DEVICES through container_cuda_visible_devices before adding the
accelerator environment variable to the Quadlet output, while leaving other
variables unchanged. Import and reuse the existing
container_cuda_visible_devices helper.

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Outside diff comments:
In `@ramalama/quadlet.py`:
- Around line 139-145: Update _gen_env to remap CUDA_VISIBLE_DEVICES through
container_cuda_visible_devices before adding the accelerator environment
variable to the Quadlet output, while leaving other variables unchanged. Import
and reuse the existing container_cuda_visible_devices helper.

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The NVIDIA container toolkit injects the device nodes of the GPUs that
were asked for, DRM nodes included. Mapping the host's GPU devices in on
top of that - /dev/dri, /dev/kfd, /dev/accel - can only add devices that
are not the accelerator in play: an iGPU on a hybrid host, or a GPU left
out of a narrowed CUDA_VISIBLE_DEVICES selection.

That was harmless while llama.cpp ran CUDA, which ignores any device it
was not given, but the Vulkan backend offloads onto every device it can
enumerate. The extra GPU is likely to be far slower than the one that
was asked for, and on a narrowed selection it is one the user asked to
keep out.

So hand the host's GPU devices over only when NVIDIA is not the
accelerator: in get_gpu_devices() for "--generate compose" and
"--generate kube", mirrored in engine.py for run and serve and in
quadlet.py for "--generate quadlet". "--device /dev/dri" still passes
them in for anyone who wants them.

Signed-off-by: Oliver Walsh <owalsh@redhat.com>
@olliewalsh
olliewalsh force-pushed the vulkan-on-nvidia-fixes branch from db67d4b to 4dee9cc Compare September 18, 2026 15:01
@olliewalsh
olliewalsh deployed to macos-installer September 18, 2026 15:01 — with GitHub Actions Active
@olliewalsh
olliewalsh deployed to macos-installer September 21, 2026 21:43 — with GitHub Actions Active
@olliewalsh
olliewalsh merged commit 39dacf9 into containers:main Sep 22, 2026
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