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[Xen-devel] issue with domains having close to or more than 512G

To: "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx>
Subject: [Xen-devel] issue with domains having close to or more than 512G
From: "Jan Beulich" <jbeulich@xxxxxxxxxx>
Date: Thu, 18 Dec 2008 10:39:04 +0000
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Keir,

the ordering of elements in the initial virtual memory arrangement is part of
the official ABI, yet I would think some parts of it may need changing:

When the complete space occupied by the initial mapping exceeds 1G,
Linux won't cope at present, and obviously as soon as it exceeds 2G it
really never can't with the current layout. 1G is reached when there is
close to 512G available to the domain. I think that the only way to deal
with this is to move the initial p2m map out of that range, at least in the
case where it would cause the entire mapping to exceed 1G (or, if
moving start_info before p2m, then 2G could be considered the limit
here, but it would require fixes to Linux anyway).

Are you aware of kernel side dependencies on this layout other than the
initial page table setup needing to be made aware of the possibility of
the p2m map sitting other than between kernel start and initial page
tables end?

Thanks, Jan


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