CONFIG_ARM64_ERRATUM_2966298 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm64

Cortex-A520: 2966298: workaround for speculatively executed unprivileged load

configname: CONFIG_ARM64_ERRATUM_2966298

Linux Kernel Configuration
└─>Kernel Features
└─>ARM errata workarounds via the alternatives framework
└─>Cortex-A520: 2966298: workaround for speculatively executed unprivileged load
In linux kernel since version 4.14.327 (release Date: 2023-10-10)  
This option adds the workaround for ARM Cortex-A520 erratum 2966298.

On an affected Cortex-A520 core, a speculatively executed unprivileged
load might leak data from a privileged level via a cache side channel.

Work around this problem by executing a TLBI before returning to EL0.

If unsure, say Y.