https://wiki.archlinux.org/title/Improving_performance#Turn_off_CPU_exploit_mitigations
Turn off CPU exploit mitigations
Warning: Do not apply this setting without considering the vulnerabilities it opens up. See this and this for more information.
Turning off CPU exploit mitigations may improve performance. Use below kernel parameter to disable them all:
mitigations=off
You would need to regenerate the grub.cfg then it presumably should work
I don’t think you actually need to remove anything from that line. Just adding mitigations=off should do.