Re: [Xen-devel] [PATCH] tools/mfn-dump: Fixes to 'dump-p2m'

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On mar, 2014-04-29 at 17:39 +0100, Andrew Cooper wrote:

> The top bit of the type has nothing to do with mappings, or certainly
> nothing that I am aware of, having successfully rewritten PV migration
> from scratch.
> 
> The guest can still have mappings to its pinned pagetables, which
> would have the top bit of the type set.
> 
> In xc_domain_save.c, this macro is used 4 times.  3 are used on mfns
> and 1 is used on a type (for a bit of debugging code which appears
> dead anyway).  I expect noone has every tried migrating a PV domain
> whose pages are located in mfns with the 44th bit set.
> 
Right. The fact that such macro is present in xc_domain_save.c was the
exact region why I was asking. :-)

> So by bogus, I mean the macro itself, and all uses of it.
> 
> My best guess is that is some vestigial code left over from a previous
> way of doing things, although I didn't encounter anything related to
> this in code archaeology I performed when trying to work out why the
> legacy migration did certain things the way they did.
> 
I see. Makes sense, thanks for clearing my doubts. :-)

Regards,
Dario

-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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