Linux kernel (drivers/iommu): When IOMMU registration fails, the core tore down groups and default domains but left

Impact

When IOMMU registration fails, the core tore down groups and default domains but left devices still flagged as using iommu-dma. Those devices then keep routing DMA setup through an iommu-dma layer whose domain is gone - a stale binding to a torn-down translation context, and a crash inside iommu-dma. On a node where the IOMMU driver failed to come up, this is the difference between failing closed and devices doing DMA with no functioning translation layer behind them.

Who can reach it

Not tenant-reachable. Triggered on the host during boot or IOMMU driver probe when iommu_device_register() fails - firmware/ACPI-table problems, a broken IOMMU unit, or a driver bug. Matters to an operator because a node in this state should be treated as having no working IOMMU at all, which means no safe device passthrough, rather than as a node that merely logged an error.

What to do

No fixed release is listed in this record; apply the linked stable commits or run a current stable/LTS kernel. Interim: fail nodes closed - if the IOMMU driver did not register cleanly, do not schedule passthrough or device-assigned workloads on that node; check dmesg for IOMMU registration failure as part of node admission.

References