Would turning off feature in kernel cause kernel module(using feature) to misbehave?

Question

I am using KVM as a kernel module. I want to turn off the huge page support. I did not find any option in KVM source to turn if off.

However, I see a kernel wide option to turn it off. If I disable a huge page feature using compile time config option CONFIG_TRANSPARENT_HUGEPAGE, the kernel source would not be able to use it, right ? Or at least fail gracefully citing missing feature ? Either of above is fine, I just wanted to know if it could have some unknown problems.

Answer 1

CONFIG_HUGETLBFS can disable the user-space API, and CONFIG_TRANSPARENT_HUGEPAGE can disable automatic creation of huge pages for generic memory. However, huge pages are an integral part of the x86 memory management code and are used for things like direct mappings or large MMIO regions. You cannot simply switch off huge pages.

When you are working with the MM code, you cannot avoid worrying about huge pages.