Re: [Xen-devel] [PATCH v5 2/4] xen/arm: introduce a generic p2m walker and use it in p2m_lookup

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Tue, 10 Sep 2013, Ian Campbell wrote:
> On Tue, 2013-09-10 at 19:00 +0100, Stefano Stabellini wrote:
> > > > -    /* This bit must be one in the level 3 entry */
> > > > -    if ( !pte.p2m.table )
> > > > -        pte.bits = 0;
> > > > +        if ( cur_first_offset != first_table_offset(paddr) )
> > > > +        {
> > > > +            if (second) unmap_domain_page(second);
> > > > +            second = 
> > > > map_domain_page(first[first_table_offset(paddr)].p2m.base);
> > > > +            cur_first_offset = first_table_offset(paddr);
> > > > +        }
> > > > +        level++;
> > > > +        if ( !second ||
> > > 
> > > ASSERT(second) seems reasonable here, I think, since it would indicate
> > > we had screwed up the p2m pretty badly.
> > 
> > I think it's possible: what if a memory range is simply missing from the
> > p2m? The second level pagetable pages could be missing too.
> 
> Then the level above it shouldn't have the valid bit set.

Oh, right!

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