Re: [Xen-devel] [PATCH v4 4/9] xen: introduce XEN_DOMCTL_devour

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 04/12/2014 10:19, David Vrabel wrote:
> On 04/12/14 00:50, Julien Grall wrote:
> > Hi Vitaly,
> >
> > On 03/12/2014 17:16, Vitaly Kuznetsov wrote:
> > > New operation sets the 'recipient' domain which will recieve all
> > s/recieve/receive/
> >
> > > memory pages from a particular domain and kills the original domain.
> > >
> > > Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
> > > ---
> > > @@ -1764,13 +1765,32 @@ void free_domheap_pages(struct page_info *pg,
> > > unsigned int order)
> > [..]
> >
> > > +        else
> > > +        {
> > > +            mfn = page_to_mfn(pg);
> > > +            gmfn = mfn_to_gmfn(d, mfn);
> > > +
> > > +            page_set_owner(pg, NULL);
> > > +            if ( assign_pages(d->recipient, pg, order, 0) )
> > > +                /* assign_pages reports the error by itself */
> > > +                goto out;
> > > +
> > > +            if ( guest_physmap_add_page(d->recipient, gmfn, mfn,
> > > order) )
> > On ARM, mfn_to_gmfn will always return the mfn. This would result to add
> > a 1:1 mapping in the recipient domain.
> >
> > But ... only DOM0 has its memory mapped 1:1. So this code may blow up
> > the P2M of the recipient domain.
> >
> > I'm not an x86 expert, but this may also happen when the recipient
> > domain is using translated page mode (i.e HVM/PVHM).
> mfn_to_gmfn() does the correct thing on x86 as it does a m2p lookup.
Is it because machine_to_phys_mapping caches the translation for dying
domain?

--
Julien Grall

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