Which of the following statements about the virtual address and physical address in the kernel can be answered?

If you have any questions about the virtual address and physical address in the kernel, which of the following can help you solve the problem? Linux general technology-Linux programming and kernel information? For more information, see the following. Catchingfish explained in one of his posts that "it is precisely because of this ing relationship that, the allocation of virtual addresses started with PAGE_OFFSET in the kernel is the allocation of physical addresses (of course, this has a certain range, which should be between PAGE_OFFSET and VMALLOC_START, and the latter is vmalloc () the start address of the memory allocated by the function) ", I don't know if I understand this.
The linear address is 4 GB space, and the real memory physical address is mapped to the linear address space starting from 3 GB. in linux, because the virtual address space is actually the same as the linear address space, the physical address + PAGE_OFFSET here is the linear address, that is, the virtual address. But what I don't understand is, how can the paging mechanism correspond to simple + operations? My mind is messy and I don't know what it means.
Which of you can answer this question with patience? 3Q