Disabling Spectre V2 Mitigations Is What Can Impair AMD Ryzen 7000 Series Performance
With SSBD being disabled via prctl(), on the AMD Ryzen 5 7600X I ran additional runs with "spectre_v2=off" to disable the Spectre V2 default mitigation and then separately "no_spectrev1" for disabling the Spectre V1 mitigation....
Quite quickly it became clear that it was the Spectre V2 mitigation in particular that when disabled is hurting the Zen 4 performance. Disabling the Spectre V1 mitigation didn't mean much for performance but when disabling Spectre V2 is where suddenly many workloads were regressing and yielding similar performance to mitigations=off.
For many different workloads, disabling the Spectre V2 mitigation on the Ryzen 7000 series was now actually hurting the performance rather than helping it...