On the kernel side there's a boot parameter for all of them: mitigations=off
Software that was compiled with additional fences may have to be recompiled to remove them.
mitigations=off disables workarounds for bugs or "mis-features" in the CPU that could be exploited to bypass OS security measures.
smap is an OS security measure, and so does not get disabled by mitigations=off. smap can be pretty draining for certain IO performance though. IMO it should be more well-known or covered by a more obvious option.
Linux kernel developers are really bad at defining and naming options like this.
https://www.kernel.org/doc/html/latest/admin-guide/kernel-pa...