Kai Huang wrote: > Intel Trusted Domain Extensions (TDX) protects guest VMs from malicious > host and certain physical attacks. TDX specs are available in [1]. > > This series is the initial support to enable TDX with minimal code to > allow KVM to create and run TDX guests. KVM support for TDX is being > developed separately[2]. A new "userspace inaccessible memfd" approach > to support TDX private memory is also being developed[3]. The KVM will > only support the new "userspace inaccessible memfd" as TDX guest memory. This memfd approach is incompatible with one of the primary ways that new memory topologies like high-bandwidth-memory and CXL are accessed, via a device-special-file mapping. There is already precedent for mmap() to only be used for communicating address value and not CPU accessible memory. See "Userspace P2PDMA with O_DIRECT NVMe devices" [1]. So before this memfd requirement becomes too baked in to the design I want to understand if "userspace inaccessible" is the only requirement so I can look to add that to the device-special-file interface for "device" / "Soft Reserved" memory like HBM and CXL. [1]: https://lore.kernel.org/all/20221021174116.7200-1-logang@xxxxxxxxxxxx/
