Is there any information on the performance impact of the microcode fix or is it too early for that?
So far the word is the microcode fix causes negligible performance impact, but using the MSR fix causes 5-15% loss. In my own testing on EPYC hardware, microcode made no noticable difference to my workloads and benchmarks. Same as random noise in results.
Planned fix
December 2023
Yikes.
It’s worth noting these are the firmware / microcode fixes.
There’s already a software solution available,
There is a software workaround, you can set the chicken bit DE_CFG[9]. This may have some performance cost, and the microcode update is preferred.
source: https://www.openwall.com/lists/oss-security/2023/07/24/3
AMD has also already released a fix for the big boy - the EPYC processor.
The MSR bit is potentially a large performance loss and AMD recommends their partners not use it. In my tests is was 5-15% on EPYC depending on workload. “Some performance cost” is really hiding the reality of that bit.
