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SubjectRe: HIGH MEMORY access
Ingo Molnar wrote:
> On Fri, 3 Mar 2000, Manfred Spraul wrote:
> > Now I'm confused: I thought that ioremap() should be used for reserved
> > memory, and kmap() for normal memory (e820: ram) with
> > page->virtual==NULL.
> well you can use kmap() for anything, not just high memory.

kmap() assumes that a "struct page" exists.

It's not guaranteed that a "struct page" exists for reserved memory:
this could happen if you boot with "mem=32M", or if the ACPI tables are
the last element in the e820 map:

* max_pfn is set to the end if the last usable block.
* then the ACPI tables follow --> they are behind max_pfn --> behind the
end of mem_map.

Not everyone has 8 GB memory :-(


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