CONFIG_RISCV_ERRATA_ALTERNATIVE is not available for thedefaultarchitecture x86.
Result is shown for architecture riscv

RISC-V alternative scheme

configname: CONFIG_RISCV_ERRATA_ALTERNATIVE

Linux Kernel Configuration
└─>CPU errata selection
└─>RISC-V alternative scheme
In linux kernel since version 5.13 (release Date: 2021-06-27)  
This Kconfig allows the kernel to automatically patch the
errata required by the execution platform at run time. The
code patching is performed once in the boot stages. It means
that the overhead from this mechanism is just taken once.