Can anyone explain the `wrmsr -a 0xc0011029 $(($(rdmsr -c 0xc0011029) | (1<<9)))`? It seems to help on my system, but I don't understand what it does, and I don't know how to unset it.
CPU designers know that some features are risky. Much like how web apps may often have "feature flags" that can be flipped on and off by operators in case a feature goes wrong, CPUs have "chicken bits" that control various performance enhancing tricks and exotic instructions. By flipping that bit you disable the optimization.
An msr is a "model specific register", a chicken bit can configure cpu features.
They don't persist across a reboot, so you can't break anything. You can undo what you just did without a reboot, just use `... & ~(1 << 9)` instead (unset the bit instead of set it).