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

To: "Santos, Jose Renato G" <joserenato.santos@xxxxxx>, "Ian Pratt" <Ian.Pratt@xxxxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] question on get_page_and_type()
From: "Ian Pratt" <Ian.Pratt@xxxxxxxxxxxx>
Date: Sun, 15 Apr 2007 05:20:01 +0100
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Thread-topic: [Xen-devel] question on get_page_and_type()
> 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


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