A while back, AMD released a whitepaper stating that the newly launched Zen 3 based Ryzen 5000 processors may be vulnerable to Spectre-like side-channel attacks due to the presence of Predictive Store Forwarding (PSF). This feature improves performance by executing instructions ahead of time by predicting the target location of loads from cache memory ahead of time. This, however, can be used by attackers if there’s a bad prediction wherein the data is dumped and the pipeline is flushed.
In line with its earlier promise, the company today rolled out a Linux kernel patch to mitigate the aforementioned side-channel vulnerability. You can now disable the feature on a Linux system by simply turning off the feature in the kernel. Although AMD keeps PSF on by default and recommends users to keep it on, you can disable it if you feel it’s not safe for your workspace.
AMD recommends leaving this feature enabled. However, we are outlining ways to disable PSF if needed.AMD
Sandboxing software is more susceptible to such side-channel exploits, so AMD is giving users the option to disable Predictive Store Forwarding. Phoronix ran some tests earlier with some patches of their own and found the performance hit of switching PSF to be less than a percent. Therefore, it doesn’t really make much of a difference whether you keep it on or off.