RE: [Xen-devel] question on get_page_and_type()

["Ian Pratt" <Ian.Pratt@xxxxxxxxxxxx>]

> Ah, OK. Thanks for clarifying!
> I assume this could only happen if the guest is buggy, right? Normally
> the guest should not do a grant_copy into its pagetables or issue a
> grant for its page tables. But in case it does it is only corrupting
> itself right? I assume only the page owner could use the page for page
> tables. Is it fair to say that the get_page_and_type() is only
> protecting a guest to harm itself? In that case would it be acceptable
> to transfer this enforcement to the guest itself if this gives a boost
> in performance?

No, for direct pagetable mode guests it's necessary for correctness,
otherwise a guest can corrupt it's pagetables and access memory
belonging to other guests or the hypervisor, or even tripple fault the
machine.

Ian

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