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

To: "Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] 32/64-bit hypercall interface
From: Hollis Blanchard <hollisb@xxxxxxxxxx>
Date: Tue, 4 Oct 2005 13:05:43 -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:
> > However, doesn't that same argument apply to correcting the
> > ABI in the first place? Shadow page tables will overshadow
> > the performance impact of making the ABI 32/64-bit clean.
> >
> > In fact, even a plain old hypercall will also overshadow that
> > performance impact, both in terms of cycle count and cache footprint.
> >
> > 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,

Would it (honest question)? Those tables aren't part of the hypercall 
interface itself, right? So as long as the hypercalls dealing with those 
tables are modified appropriately, the tables themselves don't need the 
change?

-- 
Hollis Blanchard
IBM Linux Technology Center

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