Intel Terms Ban Benchmarks on New Linux CPU Microcode

Intel has provided its microcode updates for Linux with new terms. This includes a restriction that prohibits the company from performing benchmarks on the basis of the software. The reason for this change is unknown.

The change in the conditions was implemented at the beginning of this month and has now been noticed by open source pioneer Bruce Perens, among others. Specifically, Intel writes in the terms and conditions: “User shall not publish or provide test results of software benchmarks or comparisons by itself or through any third party.” That text is not present in previous versions. Perens believes that Intel wants to prevent people from disclosing information about the performance differences that the updates entail. For example, the microcode contains patches for the recently disclosed L1TF vulnerabilities and it is known that software mitigations for this category of vulnerabilities can lead to certain performance decreases.

In the meantime, benchmarks have already been published, for example by Phoronix or Red Hat. It is unknown whether these parties have violated the conditions in the eyes of Intel by publishing the measurements. So far, there are no known signals to suggest this. Intel has not yet released an explanation for the change. The chip manufacturer has also released benchmarks of the effects of the L1TF patches. In it, it concludes that the effects are generally minimal, except in data center environments where Hyper-Threading is disabled. That’s one of the suggested mitigations.

The amended terms and conditions also have other consequences, according to reports from The Register. For example, the Debian team is having trouble with a certain other passage from the terms and conditions, forcing it to withhold the patches. Intel told the site that it sees no problems and that the terms allow distribution, but was not asked about the passage banning the publishing of benchmarks.

At first glance, the modified terms seem like a significant constraint on benchmarking, but until more is known about Intel’s motivation, there’s little to say about its implications. The limitation is in the terms of the microcode for Linux. It is not known what the terms of the microcode for Windows are. Microsoft passes that microcode into the operating system.