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Subject: Re: [Xen-devel] Re: [PATCH 2/8] xen/mmu: Add the notion of
 identity (1-1) mapping.
From: Ian Campbell <Ian.Campbell@citrix.com>
To: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
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Date: Tue, 4 Jan 2011 17:20:23 +0000
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On Tue, 2011-01-04 at 16:59 +0000, Ian Campbell wrote:
> On Tue, 2011-01-04 at 16:53 +0000, Ian Campbell wrote:
> > 
> > If I do "__set_phys_to_machine(X, X)" where X happens to currently
> > correspond to p2m_mid_missing won't that cause all pfn entries in the
> > range covered by p2m_top[topidx] (i.e. quite a few, like 512^2 pages
> > or
> > something) to switch from missing to identity? Similarly for
> > p2m_top[topidx][mididx]?
> > 
> > Perhaps ranges of identity bits are often well aligned with the
> > boundaries in the p2m 3-level tree but wouldn't that just be
> > coincidence? 
> 
> I wonder if it would make sense to have a debugfs file which exports the
> p2m, for the purposes of eye-balling it for this sort of issue?
> comparing to the e820 etc...
> 
> Maybe the whole thing in raw form would be overkill but spitting out a
> list of ranges of identity, invalid, normal pages, plus annotation
> regarding whether those come from a p2m_mid_identity style page or a
> leaf node, might be occasionally useful.

I should have read patch 5/8 first...