What's inside the kernel part of virtual memory of 64 bit linux processes?

I came upon this question : https://unix.stackexchange.com/questions/472223/whats-the-use-of-having-a-kernel-part-in-the-virtual-memory-space-of-linux-proc and based on the answer and the comments on the answer : >the kernel memory map includes a direct mapping of all physical memory, so everything in memory appears there; it also includes separate mappings for the kernel, modules etc., so the physical addresses containing the kernel appear in at least two different mappings Is this true? I couldn't find any source or reference for this, and why would it include a map of the entire physical memory and then again have a separate mapping of kernel modules? Isn't that redundant? Can someone explain in a simple manner what is inside the kernel part of virtual memory of processes in 64-bit Linux? and **please provide a source for the answer**! because I couldn't find anything related to this in any book or paper.