The memory used by the Windows kernel is either Paged or Non-Paged. Non-Paged means pinning the memory in physical RAM. Paged means it might be swapped out to disk and paged back in when needed. OP was working on BitLocker a file system driver, which handles disk IO. It must be pinned in physical RAM to be available all the times; otherwise, if it's paged out, an IO request coming would find the driver code missing in memory and try to page in the driver code, which triggers another IO request, creating an infinite loop. The Windows kernel usually would crash at that point to prevent a runway system and stops at the point of failure to let you fix the problem.

Linux is a bit unusual in that kernel memory is generally physically mapped and unless you use vmalloc any memory you allocate has to correspond to pages backed by RAM. This also ties into how file IO happens, swapping, and how Linux approach to IO is actually closer to Multics and OS/400 than OG Unix.

Many other systems instead default to using full power of virtual memory including swapping kernel space to disk, with only things explicitly need to be kept in ram being allocated from "non-paged" or "wired" memory.

EDIT: fixed spelling thanks to writing on phone.

Linux kernel memory isn’t paged out to disk, while Windows kernel memory can be: https://knowledge.broadcom.com/external/article/32146/third-...