On 5/6/22 05:44, Borislav Petkov wrote: >> Dave Hansen pointed those out in a previuos patch serie, here is the >> quote: >> >>> CXL devices will have normal RAM on them, be exposed as "System RAM" and >>> they won't have encryption capabilities. I think these devices were >>> probably the main motivation for EFI_MEMORY_CPU_CRYPTO. > So this would mean that if a system doesn't have CXL devices and has > TME/SME/SEV-* enabled, then it is running with encrypted memory. > > Which would then also mean, you don't need any of that code - you only > need to enumerate CXL devices which, it seems, do not support memory > encryption, and then state that memory encryption is enabled on the > whole system, except for the memory of those devices. CXL devices are just the easiest example to explain, but they are not the only problem. For example, Intel NVDIMMs don't support TDX (or MKTME with integrity) since TDX requires integrity protection and NVDIMMs don't have metadata space available. Also, if this were purely a CXL problem, I would have expected this to have been dealt with in the CXL spec alone. But, this series is actually driven by an ACPI spec. That tells me that we'll see these mismatched encryption capabilities in many more places than just CXL devices.
