IOMMU / SMMU DMA Isolation

When to use

• Enabling DMA isolation for a device (iommu_domain, iommu_attach_device).
• Writing or reviewing an SMMU (ARM) or VT-d (Intel) driver/configuration.
• VFIO/device passthrough in hypervisors (stage-2 DMA translation).
• Auditing whether a device can DMA anywhere (bypass/passthrough hole).
• Debugging DMA faults (translation errors, DMAR: [DMA Write] logs).
• Setting up interrupt remapping (IR table / ITS) for MSI.

When not to use

• CPU page tables (that's page-table-management).
• Devices with no DMA capability.
• Pure cache-coherency work without translation (that's dma-cache-coherency).
• Userspace buffer management.

What the agent often gets wrong