Hello !
I have found out a easy way to enable full MDS mitigation at boot with this hook:
sudo grubby --update-kernel=ALL --args=“mds=full,nosmt”
After rebooting, my x86_64-v2 cpu (intel core i5) now reports :
MDS: Mitigation: Clear CPU buffers
In case you’re interested, the documentation on MDS vulnerability/exploit is here :
https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/mds.html
Cheers! 
smart