For DMA, DMA endpoint buffers will generally be unencrypted and live in the "host domain," outside of the secure enclave running trusted code. This has been use

For DMA, DMA endpoint buffers will generally be unencrypted and live in the "host domain," outside of the secure enclave running trusted code. This has been used to construct exploits against AMD's Secure Virtualization (which relies on memory encryption), for example: https://www.usenix.org/system/files/sec19-li-mengyuan_0.pdf https://www.usenix.org/system/files/sec19-li-mengyuan_0.pdf . There are some emerging technologies like SEV-TIO and PCI-IDE which attempt to extend the trust chain down into PCIe devices, allowing trusted devices to form a relationship with trusted code in a secure execution environment: https://www.amd.com/content/dam/amd/en/documents/developer/sev-tio-whitepaper.pdf https://www.amd.com/content/dam/amd/en/documents/developer/s... Anyway, the best protection here is to terminate protocol or application-level encryption (TLS or whatever sits on top of your protocol) inside of the secure environment, so that decryption only occurs through encrypted memory. It's slower, but this way an attacker sitting as a RAM snoop could only see encrypted network traffic hit the DMA buffers, which wouldn't help them much.