Protected DMAbufs and its dynamic memory assignment woes
summary
Protected DMA-buf support targets secure media pipelines using a GStreamer pipeline with OP-TEE and must handle allocations of hundreds of MBs while keeping plaintext frames invisible to kernel/user space. Static carveouts work but waste memory; dynamic assignment requires lending normal pages to firmware and then removing kernel mappings, yet current dma_alloc_pages cannot unmap kernel pages and there’s no solid API. Explored fixes include HMM/device-private/device-exclusive approaches and a GFP-flag patch that allocates already-unmapped pages, but a reliable, efficient solution is still pending.
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chapters (8)
- 0:00Introduction to protected DMAbufs
- 3:15Secure media pipeline use case
- 6:46Kernel mainline adoption challenges
- 9:18Static memory carveouts limitations
- 10:45Dynamic memory assignment woes
- 13:58HMM and kernel page unmapping
- 18:15Memory protection and T framework
- 19:42Future confidential compute use cases
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