Explanation
It just tells you that you have Hyper-Threading (SMT) enabled, which means that a malicious guest VM could theoretically access confidential data on the host (as described in the kernel.org link you posted).
This is a hardware flaw on intel systems, and can (as far as I’m aware) only be mitigated by disabling Hyper-Threading (SMT), usually done in BIOS. Keep in mind that this incurs a (potentially hefty) performance penalty.
Reference
https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/l1tf.html