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I'm trying to organize memory a little. There are different types of memory as we see on the map returned from BIOS INT 0x15 Function 0xE820. So the way I want to organize them is by enabling paging. When creating the page tables I want to put first all the pages that have type 1 page frames, then all the pages that have type 2 page frames, and so on. The problem I run into is that the sizes of some fields are not divisible by 4096. So, for example, what would I do if I encounter a type 2 field that's 2048 bytes long? I can't skip it just like that, it may be important. But I can't make a page frame out of it because it's not long enough. If I map a page to the beginning of such a field, the last 2048 bytes of the page will hang over to the next field which may be, say, a type 4 field. So what will happen is, I'll wind up with some type 2 memory, some type 4 memory and some more type 2 memory. But that's not in order! Is there any way I can do this?

I ignore any memory that is partly reserved. This is the map for my current machine. I ignore the page at 9f000. If a page is partly reserved then I reserve it all.

I think type 2 memory might also include memory mapped I/O in which case you can't ignore it. But I'm not sure about that.

Type 2 is reserved. Don't map it. If any part of a page is reserved then treat it all as reserved.

If later on you find that some MMIO is in the reserved area map it then.

There are so many things that aren't memory. They all share the same thing: you don't have to guess where they are. You know the address in advance.