Re: [Xen-devel] [PATCH RFC v2 6/9] xen/arm: Add handling write fault for dirty-page tracing

[Jaeyong Yoo <jaeyong.yoo@xxxxxxxxxxx>]

> > > I think we'd want to establish a linear map of the current guest p2m
> > > for these purposes so we could also avoid all the map_domain_page
> > > stuff in the fault path. I think there is enough virtual address
> > > space left for that even on 32-bit, it's less critical on 64-bit
> > > anyway since we are about to have a direct map of RAM available to us.
> >
> > I think it is a good idea to have an ever-mapping linear dirty-bit map
> > for guest p2m.
> 
> By Linear map I meant slotting the p2m into the hypervisor's own page
> tables (I believe the relevant p2m and pte bits in the entries do not
> overlap, so this is possible), such that the p2m table entries are
> available at known virtual addresses and you can locate the L1, L2 and
> L3 entries corresponding to a given guest physical address with just
> arithmetic, i.e. something like:
> http://www.technovelty.org/linux/virtual-linear-page-table.html

Which virtual address range should we map the p2m? Would it be xenheap, 
domheap, or unassigned range (for instance, between  frametable and vmap)?

Jaeyong


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