[v1: Initial post] With confidential computing like TDX the guest doesn't trust the host anymore. The host is allowed to DOS of course, but it is not allowed to read or write any guest memory not explicitely shared with it. This has implication for virtio. Traditionally virtio didn't assume the other side of the communication channel is malicious, and therefore didn't do any boundary checks in virtio ring data structures. This patchkit does hardening for virtio. In a TDX like model the only host memory accesses allowed are in the virtio ring, as well as the (forced) swiotlb buffer. This patch kit does various changes to ensure there can be no access outside these two areas. It is possible for the host to break the communication, but this should result in a IO error on the guest, but no memory safety violations. virtio is quite complicated with many modes. To simplify the task we enforce that virtio is only in split mode without indirect descriptors, when running as a TDX guest. We also enforce use of the DMA API. Then these code paths are hardened against any corruptions on the ring. This patchkit has components in three subsystems: - Hardening changes to virtio, all in the generic virtio-ring - Hardening changes to kernel/dma swiotlb to harden swiotlb against malicious pointers. It requires an API change which needed a tree sweep. - A single x86 patch to enable the arch_has_restricted_memory_access for TDX It depends on Sathya's earlier patchkit that adds the basic infrastructure for TDX. This is only needed for the "am I running in TDX" part. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
