Some systems are triggering the error about missing kernel DMA remapping, despite the CPU generation being new enough and the opt-in flag being present in the DMAR ACPI table. Further debugging would be required to determine why this isn't being enabled, but on the systems we've looked at so far, none of them have any Thunderbolt ports which is what this feature is really required for.
External PCI ports have the ExternalFacingPort property in ACPI. We don't really want to be parsing ACPI tables for this, but the kernel does mark PCI bridges with external ports (ie, Thunderbolt) with this property by adding the removable attribute in sysfs (with the value removable).
We should only surface this error if:
- There are PCI bridges with external facing ports, and
- Any of these bridges are not assigned to an IOMMU.
Some systems are triggering the error about missing kernel DMA remapping, despite the CPU generation being new enough and the opt-in flag being present in the
DMARACPI table. Further debugging would be required to determine why this isn't being enabled, but on the systems we've looked at so far, none of them have any Thunderbolt ports which is what this feature is really required for.External PCI ports have the
ExternalFacingPortproperty in ACPI. We don't really want to be parsing ACPI tables for this, but the kernel does mark PCI bridges with external ports (ie, Thunderbolt) with this property by adding theremovableattribute in sysfs (with the valueremovable).We should only surface this error if: