[fjvbn2003]

Problem

GPU Feature Discovery (k8s-device-plugin v0.19.3, deployed by GPU Operator v26.3.3) prints this line every time it relabels a node, on every node, for every GPU that is bound to the nvidia driver:

2026/10/17 14:14:25 WARNING: unable to detect IOMMU FD for [0000:01:00.0 open /sys/bus/pci/devices/0000:01:00.0/vfio-dev: no such file or directory]: %!v(MISSING)

There are two problems in pkg/nvpci:

1. getIOMMUFD() returns the ReadDir error when <device>/vfio-dev does not exist, and getGPUByPciBusID() logs it as a warning. The kernel only creates vfio-dev for a device that is bound to a VFIO driver on a kernel with VFIO device cdev support. For a GPU that is bound to nvidia, which is the common case, a missing vfio-dev directory is expected and there is no IOMMU FD to report.
2. simpleLogger.Warningf() passes the variadic slice as one argument (log.Printf("WARNING: "+format, v)), so every warning that goes through the default logger is garbled: the arguments are printed as one [...] list and the last verb becomes %!v(MISSING).

Measured on five single-GPU nodes (RTX 4070 Laptop x2, RTX 4060 Laptop, RTX 3060 Laptop, RTX 3090) with GFD's default 60 s sleep interval, over the last 24 hours:

Node	GFD log lines	unable to detect IOMMU FD	%!v(MISSING)	Creating Labels
A	5752	1438	1438	1438
B	5752	1438	1438	1438
C	5752	1438	1438	1438
D	5744	1436	1436	1436

One line in four of the GFD log is this warning.

Changes

• getIOMMUFD() returns "", nil when vfio-dev does not exist. Other errors, and an existing vfio-dev directory without a vfio* entry, are still reported as before.
• simpleLogger.Warningf() forwards the arguments with v....
• Tests: TestNvpciIOMMUFDNotBoundToVFIO (no vfio-dev → empty IommuFD, no warning), TestNvpciIOMMUFDEmptyVFIODev (the remaining warning is still logged, with the expected text), and TestSimpleLoggerWarningf.

Testing

$ go test ./pkg/nvpci/ -run 'TestSimpleLogger|TestNvpciIOMMUFD' -v
--- PASS: TestSimpleLoggerWarningf
--- PASS: TestNvpciIOMMUFD
--- PASS: TestNvpciIOMMUFDNotBoundToVFIO
--- PASS: TestNvpciIOMMUFDEmptyVFIODev
$ go test ./...
ok  ... (all packages)

Without the change, TestSimpleLoggerWarningf fails with the same [...]: %!v(MISSING) output as above, and TestNvpciIOMMUFDNotBoundToVFIO fails because the warning is logged.

I did not run golangci-lint locally.

GFD gets the fix with its next go-nvlib bump.

I used an AI assistant (Claude) to help investigate and write this change, including the tests described above.

🤖 Generated with Claude Code

[rajatchopra]

Comment on line 351 needs to be edited, in that case.

[fjvbn2003]

Good catch, thanks. After this change a missing vfio-dev directory returns "", nil from getIOMMUFD, so it never reaches this branch and "this host may not have iommufd configured/supported" no longer describes when the warning is logged. I updated the comment in a18c634: the missing-directory case is handled in getIOMMUFD, and the errors that still get here are only logged because the IOMMU FD is optional. go test ./... passes locally.

(Written with help from Claude (AI).)