Re: [Xen-devel] "Iomem mapping not permitted" during windows crash dump under GPLPV

[Tim Deegan <Tim.Deegan@xxxxxxxxxx>]

At 13:30 +0000 on 02 Feb (1265117447), Keir Fraser wrote:
> On 02/02/2010 11:27, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:
> 
> >>>> "James Harper" <james.harper@xxxxxxxxxxxxxxxx> 02.02.10 12:07 >>>
> >> Someone on the ntdev list suggested that one approach could be to
> >> allocate a single page at setup time and map that into each 'hole' I
> >> leave behind by ballooning pages out. I haven't checked if Xen supports
> >> a HVM DomU randomly mapping pages like that and if it will let it map
> >> the same page multiple times, but it would remove the errors and keep
> >> everything happy.
> > 
> > There is no question - it just has to support this. Linux would not work
> > without this (nor can I imagine any other OS would).
> 
> I don't think a page can be simultaneously mapped at multiple locations in a
> guest's p2m though.

No, the basic p2m code doesn't allow aliasing (because it tries to
maintain a coherent m2p table).  The recent page-sharing patches from
Grzegorz Milos relax that restriction, though IIRC only for explicit
sharing operations managed by dom0.  I'm sure it could be extended to
cover this case.

What's the problem with just ignoring the errors when a frontend page
doesn't exist, though?

Cheers,

Tim.

-- 
Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, Citrix Systems (R&D) Ltd.
[Company #02300071, SL9 0DZ, UK.]

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel