Post #4038131
2026-07-23 13:59 UTC
@dalias@hachyderm.io FireWire has direct DMA access to the host’s memory (up to the 4 GB address space on most implementations), which is why it earned that reputation. In many ways, it became the scapegoat.
You know what else has DMA? PCI Express. Every GPU, NVMe SSD, NIC, and Thunderbolt device.
The real issue was that, at the time, IOMMUs either didnt exist or werent widely deployed or enabled.
The driver will use the IOMMU after few round of refactoring. My priority was to get the driver correct and working on real hardware first. And get it out the deprecation list.
Replies (1)
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@dalias@hachyderm.io 2026-07-23 14:07
@seuros@mastodon.bsd.cafe Right, but in those other cases, the device in question was a fixed installation inside the computer's enclosure that you had chosen to trust, not an external device. I've always deemed bus-mastering DMA a design flaw in all of those other things too, though IOMMU mostly fixed it on hardware new enough to have an IOMMU that's an actual security boundary and not just advisory like some early ones were. None of this detracts from what you're doing, and I'm glad you'll be wiring up the IOMMU stuff.