Cooperative DMA in a memory-oversubscribed environment
summary
Proposes making IOMMU page tables dynamic by adding a new ioctl VFIO_MAP_DMA_UNPINNED, hooking VFIO into MMU notifiers and an IOMMU domain callback remap_pte so host mirrors user page-table changes instead of pinning upfront. Adds a lightweight guest cooperative protocol where the guest does a CPU touch before DMA to fault pages in (and a shared bitmap to prevent swap-out), aiming to avoid PRI/SVA hardware and reduce VM‑exits to the first fault; notes race, THP and notifier-coherence challenges and this is an RFC-stage design, not yet implemented.
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chapters (9)
- 0:00Introduction
- 0:29Overview
- 0:57Hardware
- 3:16DMA Unpinned
- 6:05Feedback
- 12:12IOMU
- 13:04Exposure
- 13:59Summary
- 17:49Wrapup
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