Re: [Xen-devel] get_page_from_gfn() for foreign pages

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
[snip]
> >> And then you didn't really answer my question.
> >
> > Well, you can't revoke a grant whist a backend has it mapped... that's been
> > a limitation forever. Also, I think it's reasonable that granting to a 
> > domain
> > A allows domain A *and* any other domain with mapping privilege over
> domain A
> > to access that page. I don't think there's really any expectation in the
> > grant interface that granting to only that domain... frontends have to trust
> > backends and if the backend grants it on then so be it. That's certainly the
> > level of trust that's been in place since v2 and AFAIK no-one is unhappy
> about
> > that.
> 
> All true, but what you want to do here is a mapping outside of
> what grant_table.c controls and provides. Yet for the page owner
> to know when a grant is fine to revoke, such obtaining of extra
> references would need to be tracked.
> 

Ah yes, that's a bit gnarly. I'll have to try to figure out what can be done 
there.

  Paul

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