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Re: [Xen-devel] [V7 PATCH 5/7] pvh: change xsm_add_to_physmap

On Mon, 2014-02-10 at 15:33 +0000, Julien Grall wrote:
> On 02/10/2014 03:27 PM, Ian Campbell wrote:
> > Wouldn't it be incorrect to generically return OK for mapping a
> > DOMID_XEN owned page -- at least something needs to validate that the
> > particular mfn being mapped is supposed to be shared with the guest in
> > question.
> It's already the case. By default a xen heap page doesn't belong to
> DOMID_XEN. Xen has to explicitly call share_xen_page_with_privileged
> guess (see an example in xen/common/trace.c:244) to set DOMID_XEN to the
> given page.

Ah, I didn't know this.

> > TBH, it doesn't seem that this mechanism for sharing xenpages with
> > guests is a good fit for PVH or HVM guests/dom0. Perhaps a specific
> > mapspace would be more appropriate?
> Following my explanation just above, I don't think we need to have a
> specific mapspace. XSM and DOMID_XEN will already protect correctly the
> mapping of xen heap page.


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