Comment 466 for bug 1690085

There are two solutions or workarounds that have been reliable for me, one of which I now trust more than the other.

First, if your BIOS has the option for 'Power Supply Idle Control' hiding somewhere in its settings (generally in a sub-menu off an 'advanced' menu), setting it to 'Typical current idle' seems to work. I trust this workaround more than the next one, but it requires a BIOS that has been updated to include AGESA 1.0.0.2a (AGESA is apparently a magic blob that AMD supplies to vendors).

Before I had the BIOS option available, I also had a stable system by using the kernel command line parameters 'rcu_nocbs=1-15 processor.max_cstate=5' (some people use 1 as the maximum cstate). This requires a kernel that supports rcu_nocbs, which not all kernels are built to do, and is more magical than the BIOS setting; it's clear that these settings are stabilizing the system through some side effects, not their direct operation.

(I experimentally determined that on my hardware and setup, merely using 'processor.max_cstate=5' wasn't enough; my machine still locked up.)

My machine runs Fedora 27, using Fedora 4.16.x and 4.17.x kernels on a Ryzen 1800X on an ASUS Prime X370-PRO motherboard with ECC RAM, currently using BIOS 4011.