This is somewhat of a necro of AMD Microcode updates not working?, but that thread seems to have died.
In light of the recent AMD speculative execution bugs (yes, more of them), my dmesg has started saying:
tlater ~ $ dmesg | grep microcode
[ 0.407693] Speculative Return Stack Overflow: IBPB-extending microcode not applied!
[ 0.407694] Speculative Return Stack Overflow: Mitigation: safe RET, no microcode
Since I have hardware.cpu.amd.updateMicrocode set, I figured this would long have been fixed, so I guessed I needed a BIOS update or such, but after applying it that hasn’t fixed the problem.
I checked my cpuinfo:
tlater ~ $ grep 'model\|microcode' /proc/cpuinfo
model : 33
model name : AMD Ryzen 5 5600X 6-Core Processor
microcode : 0xa201025
The latest appears to be 0xaa00212.
This is a bit concerning, lots of NixOS systems will be vulnerable to that speculative execution bug, despite users believing they are mitigating it. Does anyone have any idea what’s going wrong?