все так отключают или много натулено?
Add either mitigations=off or that long one-liner to your /etc/sysconfig/grub and re-generate grub's configuration file with grub2-mkconfig (your distributions procedure will vary) and you're all set. Do note that the latest editions of stable branch kernels (4.14.x, 4.19.x) do have a mitigations= parameter so that alone is enough on kernels newer than 5.1.13 and later versions of stable branch kernels such as 4.19.60+.