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

["Santos, Jose Renato G" <joserenato.santos@xxxxxx>]

Yes, of course. Thanks, Ian.
I am not thinking straight (Tired, working late to finish the slides for
the summit). 
Regards
Renato 

> -----Original Message-----
> From: Ian Pratt [mailto:Ian.Pratt@xxxxxxxxxxxx] 
> Sent: Saturday, April 14, 2007 9:20 PM
> To: Santos, Jose Renato G; Ian Pratt; xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: RE: [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 machine.
> 
> Ian
> 

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