Question regardin intel64 arch and page table setup

H. Peter Anvin hpa at
Wed Aug 11 21:53:13 EDT 2010

On 08/11/2010 06:05 PM, Neil Horman wrote:
> Thanks for all the info, guys.  I hadn't considered that we couldn't access the
> 64 bit startup point for the bzImage.  I just figured we could jump to
> startup_32 + 0x200 in the bzImage header once I had the page table bit set up
> properly.
> I hadn't considered the problems we might encounter with driver issues loading
> above 4gb and what have you, nor the starting of AP's.  
> Regardless, I'll keep tinkering.  One more question.  When setting up the page
> table in the panic boot case, is it sufficient to setup an identity map for the
> pages in the reserved crashkernel range, or do we need to identity map the
> entire range of ram?
> Best
> Neil

One thing... if the crashkernel reservation can be made non-contiguous,
it probably doesn't require a whole lot of memory below 1 MiB (a handful
of pages) and below 4 GiB (probably less than a megabyte) to achieve
full functionality.  It just means that the crashkernel has to operate
with a true memory map for its reservations.


H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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