sIOPMP: Scalable and Efficient I/O Protection for TEEs

Trusted Execution Environments (TEEs), like Intel SGX/TDX, AMD SEV-SNP, ARM TrustZone/CCA, have been widely adopted in prevailing architectures. However, these TEEs typically do not consider I/O isolation (e.g., defending against malicious DMA requests) as a first-class citizen, which may degrade the I/O performance. Traditional methods like using IOMMU or software I/O can degrade throughput by at least 20% for I/O intensive workloads. The main reason is that the isolation requirements for I/O devices differ from CPU ones. This paper proposes a novel I/O isolation mechanism for TEEs, named sIOPMP (scalable I/O Physical Memory Protection), with three key features. First, we design a Multi-stage-Tree-based checker, supporting more than 1,000 hardware regions. Second, we classify the devices into hot and cold, and support unlimited devices with the mountable entry. Third, we propose a remapping mechanism to switch devices between hot and cold status for dynamic I/O workloads. Evaluation results show that sIOPMP introduces only negligible performance overhead for both benchmarks and real-world workloads, and improves 20% 38% network throughput compared with IOMMU-based mechanisms or software I/O adopted in TEEs.