Comment by nine_k
2 days ago
Not memory management unit (MMU), but I/O memory access management unit (IOMMU). That is, can a device start a DMA transfer from/to anywhere in the physical RAM? Does this access have to pass through virtual address translation? For stuff like GPUs and even NICs the performance implications can be noticeable.
Yeah, not a big fan either. I also saw some suggestion that current implementations of IOMMUs aren't highly secure. Performance is always the big opponent to security. I wrote about my thoughts on not necessarily relying on IOMMUs adjacent to this reply: https://news.ycombinator.com/item?id=43122900.