Re: [Xen-devel] PV guest + shadow paging

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

Keir Fraser wrote:
> On 24/10/07 11:00, "Jeremy Fitzhardinge" <jeremy@xxxxxxxx> wrote:
>
>   
>> Tim Deegan wrote:
>>     
>>> The joy of NPT(VMI?)/EPT is that you don't need shadow pagetables at
>>> all. :)
>>>   
>>>       
>> Sure, but from a guest interface perspective they look the same.
>>     
>
> Would you want to take advantage of NPT/EPT once you've pv'ed your mmu
> interfaces?
>   

I think so.  NPT/EPT would seem to have all the advantages of shadow
paging and direct paging without the disadvantages.  We would avoid
taking faults/hypercalls on pagetable updates, and have the secondary
benefit of not needing to worry about page permissions on pagetables,
making it easier to use superpages for the kernel and in general. 
Perhaps the initial implementations will be sufficiently poor that it
isn't worth doing now, but I think it will in time.

    J

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