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Re: [Xen-devel] [PATCH 2/3] x86: real mode support: get EDD info

To: Jan Beulich <jbeulich@xxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH 2/3] x86: real mode support: get EDD info
From: Keir Fraser <keir@xxxxxxxxxxxxx>
Date: Fri, 02 Mar 2007 11:15:44 +0000
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On 2/3/07 10:32, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote:

> Obtain EDD info from BIOS and pass it up to Dom0.

What data format are the EDD/EDID buffers filled with? The format is not
defined in the public headers. Is it simply whatever Linux happens to be
using internally?

I am still interested in trying out an interface to let dom0 request code to
be run in various modes and on various CPUs. This would be attractive in
this case, assuming that these BIOS calls could be made later than very
early bootstrap, as it would avoid piling code into Xen, and assumptions
about info data formats, just because of the environment that the
interrogating code needs to be executed in. No doubt it is a larger initial
amount of engineering effort up front though. Also I'm not sure if there
would be any subtle gotchas to running this skanky BIOS code later in the
boot sequence (I'd be optimistic that it'd just work though).

 -- Keir

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