Check, whether VK_DRIVER_FILES works standalone (without registry registration)

[jakoch]

The PR #545 added support for exporting the VK_DRIVER_FILES environment variable.
This was released with v1.3.0.

But the CI pipeline was initially failing due to missing driver registration, even with VK_DRIVERS_FILES set as env var.
So i restored the traditional registry-based driver setup alongside the new export logic to get CI green.

We need to figure out, if Vulkan can discover and load drivers using VK_DRIVER_FILES only
without setting the driver up using registry registration.

[Firestar99]

See TLDR: #547 (comment)

Log of my observations from testing in rust-gpu. We only use swiftshader in "CI / Difftest (windows-2022)":

• In ci: fix swiftshader rate limit exceeded Rust-GPU/rust-gpu#506 I've removed us explicitly setting VK_DRIVER_FILES and we don't add any registry entry to register the driver, and it succeeds
• Vulkan sdk output branch (commits are stacked):
  • Rust-GPU/rust-gpu@29f7fe3 I've added the vulkaninfo step 1:1 from this repo, yet it fails not writing the profile.json. Outputs this warning:

  D:\a\rasterizers\rasterizers\swiftshader\src\Vulkan\libVulkan.cpp:648 WARNING: UNSUPPORTED: pCreateInfo->pNext sType = 1000011000

  • Rust-GPU/rust-gpu@3310bf1 I additionally copied your swiftshader driver registration, which fails the exact same way
  • Rust-GPU/rust-gpu@2eff82b I switched from windows-2022 to windows-2025 and it succeeds?
    -> will be using windows-2025 from now on
• Vulkan sdk output branch 2 (new commit stack):
  • Rust-GPU/rust-gpu@ebcaa1b using windows-2025
  • Rust-GPU/rust-gpu@c10a406 and the vulkaninfo step, without driver registration fails
    -> vulkan driver registration seems to be required for vulkaninfo, but not for rust-gpu difftests (based on wgpu). vulkaninfo prints Using Vulkan Loader C:\Windows\SYSTEM32\vulkan-1.dll, could wgpu (webgpu API and runtime) configure ash (rust vulkan wrapper) to somehow load it differently? It's not embedding it (feature "linked" is disabled).
• Updating main branch to windows-2025
  • Rust-GPU/rust-gpu@ebcaa1b updating to windows-2025 fails
    -> Seems like vulkan driver registration is only optional on windows-2022, and required on windows-2025 (and windows-latest).

[jakoch]

Given the error message
swiftshader\src\Vulkan\libVulkan.cpp:648 WARNING: UNSUPPORTED: pCreateInfo->pNext sType = 1000011000
it seems to be a SwiftShader issue and should be reported upstream.

Vulkaninfo is started, the driver is found and the instance is created, but the requested driver capability is not there.
So a warning is emitted that a missing/not yet recognized new sType exist, which probably expands the VK spec.
Even if a VK feature is unsupported, it should be recognized.

[Firestar99]

TLDR: Only on windows-2022 you don't need to register the vulkan driver, this doesn't work on windows-2025.

It would be nice to have automated registration in this action, so users don't have to think about it.

[jakoch]

This note explains the reasoning behind:

• The rollback of VK_DRIVER_FILES.
• The rollback of adding rasterizers to the PATH variable.

Why the rollback of VK_DRIVER_FILES?

Setting VK_LOADER_DEBUG=error,warn,info before running vulkaninfoSDK.exe was a good step.

What’s important and missing in the follow-up after sharing your observations is this:

INFO:              Loader is running with elevated permissions. Environment variable VK_LOADER_LAYERS_ENABLE will be ignored
INFO:              Loader is running with elevated permissions. Environment variable VK_LOADER_LAYERS_DISABLE will be ignored
INFO:              Loader is running with elevated permissions. Environment variable VK_LOADER_LAYERS_ALLOW will be ignored
INFO:              Loader is running with elevated permissions. Environment variable VK_LOADER_DRIVERS_SELECT will be ignored
INFO:              Loader is running with elevated permissions. Environment variable VK_LOADER_DRIVERS_DISABLE will be ignored
INFO:              Loader is running with elevated permissions. Environment variable VK_DRIVER_FILES will be ignored
INFO:              Loader is running with elevated permissions. Environment variable VK_ICD_FILENAMES will be ignored
INFO:              Loader is running with elevated permissions. Environment variable VK_ADD_DRIVER_FILES will be ignored

This highlights two things:

• The runners are operating in elevated mode.
• Any environment variables, including VK_DRIVER_FILES, will be ignored.

All Windows runners run as admin with UAC off.
Ref. GitHub Actions - Github Hosted Runners - Administrative privileges

Because of this, VK_ICD_FILENAMES (deprecated), VK_DRIVER_FILES, and VK_ADD_DRIVER_FILES are all ignored when running Vulkan applications with elevated privileges.
Ref. Vulkan Loader Documentation

And if it worked on one runner, that could be due to differences in UAC strictness between runners.

So, i guess, the answer i was looking for is:
Vulkan can not discover and load drivers using the VK_DRIVER_FILES override in a CI context standalone,
because of permission elevation, making the VK_DRIVER_FILES approach incompatible.

Why the rasterizers were removed from the PATH variable?

After registering, the location of the DLLs is already known via the chain: ICD → registry → JSON → DLL.
But, i think, sharing these paths in the logs can still be very useful, as users may want to place the DLLs alongside their executables for distribution.

Automatic entry into Windows Registry

After reverting the PR, I’ve added automatic registration of the ICD in the Windows registry.

This approach is less explicit but simplifies setup by removing the need for a manual registration step.

- if: ${{ runner.os == 'Windows' }}
  name: Windows - Register Driver in Registry
  shell: pwsh
  run: |
    reg add "HKLM\SOFTWARE\Khronos\Vulkan\Drivers" /v "ICD" /t REG_DWORD /d 0 /f

[jakoch]

Changes released with v1.4.0.