In 2022, AMD cautioned customers that Ryzen systems running Windows 10 and 11 could experience intermittent stuttering if the Firmware Trusted Platform Module (fTPM) were used. Initially, this only occurred with Windows users; however, it has now spread to Linux devices that have enabled the AMD fTPM RNG by default – starting with version 6.1+. Not only is it happening in both operating systems but also across many newer models too!
AMD’s recent article suggests that certain Ryzen system configurations may experience temporary pauses in interactivity or responsiveness due to extended fTPM-related memory transactions performed on Windows 10/11. This occurs within the SPI Flash Memory (“SPIROM”) located on the motherboard.
To avoid the fTPM issue, AMD urges customers to update their motherboard system BIOS or opt for an alternative hardware TPM solution. The problem should be rectified once they use the AGESA 1207 version of AMD or a more advanced one.
Sadly, many laptop providers and system vendors have been slow to release BIOS updates that would help resolve this issue. With Linux 6.1+ now utilizing AMD fTPM’s random number generator by default, users are beginning to experience stuttering on their systems as a result.
These past two weeks have been devoted to a full assessment of this issue and its resolution. Thankfully, the development team has now generated a patch that will be introduced in the mainline kernel: it disables any hardware random number generator from being employed on systems with perilous fTPM versions.
Exclaiming the significance of today’s kernel patch sent straight to Linus Torvalds, AMD Linux engineer Mario Limonciello expressed:
AMD has notified computer manufacturers that “stuttering” can arise if the fTPM is enabled in BIOS. Fortunately, newer versions of the firmware have resolved this issue; however, it’s now up to system designers whether they will share these updated patches or not.
Since the introduction of kernel 6.1, with its commit b006c439d58db (“hwrng: core – start hwrng kthread also for untrusted sources”), this issue has become increasingly common due to fTPM’s default usage in /dev/hwrng. Unfortunately, all applications utilizing this device have been suffering from unacceptable stuttering as a consequence.
To prevent further issues, turn off the registration of faulty hwrng when detecting these broken fTPM versions.
With anticipation, Torvalds should accept the patch this week in preparation for Linux 6.2’s stable release on Sunday. Additionally, it will be back-ported to the Linux 6.1 LTS series too.