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Re: [Xen-devel] 32/64-bit hypercall interface -- p2m tables

To: "Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] 32/64-bit hypercall interface -- p2m tables
From: Hollis Blanchard <hollisb@xxxxxxxxxx>
Date: Tue, 4 Oct 2005 16:16:47 -0500
Cc: Jeremy Katz <katzj@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, Ian Pratt <Ian.Pratt@xxxxxxxxxxxx>, "Nakajima, Jun" <jun.nakajima@xxxxxxxxx>
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On Monday 03 October 2005 17:03, Ian Pratt wrote:
> > So if your choice then is between a compatibility translation
> > layer and altering the interface, I think it's pretty clear
> > that changing the interface will result in the least amount
> > of additional code (and associated long-term code maintenance).
>
> This would result in doubling the size of the all the p2m and m2p
> tables,

I don't believe this is true. The tools can create those tables as arrays of 
32- or 64-bit mfns depending on the bitsize of the domain being created.

Xen would also know the bitsize of the domain, and so could treat the tables 
as 32- or 64-bit as needed. That of course only matters if people actually do 
the work to run 32-bit domains on 64-bit hypervisor. Fixing the ABI enables 
that work, should people want to pursue it later.

-- 
Hollis Blanchard
IBM Linux Technology Center

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