PLEASE ONLY DO THIS IF YOU KNOW WHAT YOU’RE DOING! THIS IS A SECURITY RISK!

Disabling is pretty straightforward. Edit your grub configuration:

# vim /etc/default/grub

Find the line that starts with GRUB_CMDLINE_LINUX and add the following parameters at the end:

noibrs noibpb spectre_v2=off spec_store_bypass_disable=prctl spec_store_bypass_disable=off nospectre_v1

Afterwards, recreate your bootloader configuration. How to do this depends on your distribution. Usually, you either use update-grub or grub2-mkconfig. Check whichever is installed on your system. Note that at least forfor grub-mkconfig you’ll need to set a proper output if your on an UEFI system. It will default to creating a BIOS configuration. For Fedora the command looks like this:

# grub2-mkconfig --output=/boot/efi/EFI/fedora/grub.cfg

Reboot and you’re done. Check the results using this tool.

UPDATE: This does not disable all the security features. Will need some further investigating.