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Re: [Xen-devel] arch_set_info_guest() and cr1

(old mail, I know)

On Sat, 2011-08-13 at 03:17 +0100, Jeremy Fitzhardinge wrote:
> On 08/12/2011 03:01 PM, Mukesh Rathor wrote:
> > Ah I see it, during save/restore, it is used. 
> > Well, I'm trying to keep the option of using PV paging with hybrid, so 
> > I may need to honor that. But that's phase 2.
> Though it would be nice to re-enable the use of PV writable pagetables
> to get access to HAP, and we could do without that.
> Does Xen require that the user pagetable be a proper subset of the
> kernel pagetable?  If we can assume that and get proper ring protections
> in the HVM container, then we can simply ignore the user pagetable (and
> would have to if we want to get good syscall performance).

IIRC back when I did the (now completely defunct) supervisor mode kernel
stuff that was exactly the assumption which was made and it certainly
worked in practice (although "require" might be a strong term).


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