Re: HIGH MEMORY access

From: Manfred Spraul (manfreds@colorfullife.com)
Date: Fri Mar 03 2000 - 09:32:18 EST


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 :-(

--
	Manfred

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