Googlers have not only figured out how to break AMD’s security – allowing them to load unofficial microcode into its processors to modify the silicon’s behavior as they wish – but also demonstrated this by producing a microcode patch that makes the chips always output 4 when asked for a random number.
And this ability to change the microcode not only allows Google and others to customize the operation of their AMD chips, for good and non-good reasons, but it also smashes the Epyc maker’s secure encrypted virtualization and root-of-trust security features.
Background
Microcode is a special block of programs typically loaded into a processor during system startup that defines the way the chip works. By providing microcode to users, AMD can add some features, fix certain…