I don't believe Intel (whose implementation of encryption this targets) have an IOMMU for PCIe. For UPI (or whatever inter-socket protocol is going on), it wouldn't make sense to have an IOMMU since cores need permission to do arbitrary reads anyway.
There are plenty of cheats that are seemingly impossible to detect. I play Team Fortress 2 and there's at least one cheat there that, from what I've read, uses code that's unique to each instance used by a cheater. VAC seems to scan for code signatures so it doesn't detect it.
This hardware cheat makes it even harder to detect since it reads and writes directly to main memory using DMA. No drivers or software needed at all. All you possibly could detect is the PCI-ID(which can be changed) and possibly the DMA if there's an IOMMU.
No, I mean that, if the IOMMU is off or if it allows access to an address, then MKTME will treat that access exactly as though it was a normal access from the CPU. So, if the device selects the right key (the key uses some otherwise unused physical address bits), then the device will access the decrypted data.
