Users cry foul after AMD stripped memory crypto from its consumer CPUs

HSI output showing that his Ryzen CPU once provided TSME but no longer does. AMD pulled the feature for consumer CPUs without notice or an easy means for users to know.

Credit: Ben Kilpatrick

This sent Kilpatrick into a monthslong investigation to figure out what had happened. After sending an inquiry to both the support and engineering teams at MSI, the manufacturer of his motherboard, he finally convinced company engineers to run tests.

They found that consumer versions of Ryzen running on MSI and Gigabyte motherboards had TSME enabled when an older firmware version, available exclusively through the AMD Generic Encapsulated Software Architecture (AGESA), described here, was used during the boot process. When the firmware in a newer AGESA, specifically version 1.2.7.0, ran instead, TSME showed as “not supported.” Pro versions of the Ryzen CPU supported TSME across both motherboards and AGESA versions.

“The big outstanding question is whether this is a deliberate policy decision by AMD to restrict TSME to PRO chips, or an unintentional regression that was introduced in AGESA 1.2.7.0,” Kilpatrick told Ars. He continued:

The reason that distinction matters is that if it is deliberate policy, AMD made a conscious decision to remove a working feature from consumer hardware and restrict it to enterprise customers. If it is an accidental regression, it is a firmware bug that AMD should fix. Either way the silicon is capable, either way the change happened in AGESA, and either way AMD has declined to explain it. But the two scenarios imply very different things about exactly what happened.

As part of his investigation, Killpatrick filed a bug report on AMD’s public engineering GitHub repository. Two AMD engineers engaged directly.

Tom Lendacky, an AMD fellow software engineer, replied that he didn’t know what caused the change. He suggested disabling and then re-enabling the option in the BIOS. “If that doesn’t work, my guess would be that it is a BIOS issue and you would want to contact MSI,” (It was this suggestion that led Kilpatrick to prevail upon MSI engineers to run the tests mentioned earlier.)

Mario Limonciello, AMD senior principal software engineer and maintainer of the fwupd version of HSI, then chimed in. He, too, suggested disabling and re-enabling the BIOS settings. “If it still doesn’t work; then yes please report it to your board vendor to debug,” he said.