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Re: [Xen-devel] [RFC] change provided physical RAM map to add EBDA

To: Guillaume Thouvenin <guillaume.thouvenin@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] [RFC] change provided physical RAM map to add EBDA
From: Alan Cox <alan@xxxxxxxxxxxxxxxxxxx>
Date: Thu, 15 Mar 2007 11:57:22 +0000
Cc: Xen devel ML <xen-devel@xxxxxxxxxxxxxxxxxxx>, Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>
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> Yes I think you're right, EBDA seems always located at 0x40E in physical

0x040E physical contains either the real mode segment of the EBDA at
0x40E or may be zero on some systems if no EBDA block is present. On the
same machine you'll sometimes find the EBDA vanishes or appears depending
upon whether a PS/2 mouse is plugged in which can be handy for debug.

> My idea is to map the real memory region that contains EBDA to dom0. So
> dom0 will see the real machine memory region under 640Ko (0xa0000) in is
> own physical map. 

This would be useful, and also useful for things like emulators.


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