CONFIG_RISCV_ISA_SVPBMT is not available for thedefaultarchitecture x86.
Result is shown for architecture 64BIT or riscv

Svpbmt extension support for supervisor mode page-based memory types

configname: CONFIG_RISCV_ISA_SVPBMT

Linux Kernel Configuration
└─>Platform type
└─>Svpbmt extension support for supervisor mode page-based memory types
In linux kernel since version 4.14.326 (release Date: 2023-09-23)  
Adds support to dynamically detect the presence of the Svpbmt
ISA-extension (Supervisor-mode: page-based memory types) and
enable its usage.

The memory type for a page contains a combination of attributes
that indicate the cacheability, idempotency, and ordering
properties for access to that page.

The Svpbmt extension is only available on 64-bit cpus.

If you don't know what to do here, say Y.