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Re: [Xen-devel] [PATCH v3 5/6] ioreq-server: add support for multiple servers

At 14:52 +0000 on 17 Mar (1395064322), Paul Durrant wrote:
> > -----Original Message-----
> > From: Ian Campbell
> > I don't suppose there is any way to pull these pages out of the guest
> > pfn space while still accounting them to the guest. Or if there is it
> > would probably be a whole other kettle of fish than this series.
> > 
> The closest analogy I can think of accounting-wise would be shadow
> pages. I'll have a look at how they are handled.

It should be much simpler than shadow pages _provided_ that nobody
adds a XENMAPSPACE namespace that uses real MFNs.  Shadow pages have
to be accounted weirdly becaus ethey can't be owned by the guest or PV
guests could just map them.

As long as we stick to the rule that all HVM-guest operations have to
go through the p2m, and we don't let the guest map pages by MFN, then
removing it from the p2m is enough to stop the guest accessing it.

Of course, for security purposes we ought to treat the device-model
process/stubdom as being under guest control anyway - hence the
stubdom qemu.


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