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[Zack Mitchell]

The first thing I’d verify before blaming the IOMMU itself is whether it’s actually wired up in your boot path, because that’s where the vast majority of “DMA still works” reports fall apart. On AMD systems, Secure Memory Encryption (SME/SEV) and IOMMU isolation both hinge on SVM being enabled in BIOS and amd_iommu=on being passed to the kernel (check dmesg | grep -i iommu for “AMD-Vi: IOMMU performance limits” or “enabled” messages). On Intel, you need VT-d enabled in BIOS plus intel_iommu=on, and critically, many boards ship with the IOMMU enabled in firmware but disabled at the group level — so even with the kernel flag set, devices in the same DMA alias group still share access. Check `dmesg | grep -i dm

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