Re: why xen use x86_emulation() in page_fault

[Christoph Egger <Christoph.Egger@amd.com>]

On 10/13/11 13:47, Tim Deegan wrote:
> At 21:07 +0800 on 11 Oct (1318367233), cc Luit wrote:
>>>> Why don't you just use EPT/NPT instead of shadow pagetables?  That code
>>>> is a lot simpler and the end result is easier to validate than shadow
>>>> pagetables are.  Is it particularly important to support shadow
>>> pagetables?
>>>
>> yeah, we have consider that, and of course the EPT is much more convenient,
>> BTW, do you know is there any simulator that can well support EPT of xen?
>> the shadow page's problem is a little relevent to the selection of
>> simulator~
>
> There's experimental support in Xen itself for running a hypervisor
> inside a HVM guest.  On AMD, that includes (and indeed requires) NPT in
> the guest hypervisor.

Not quite right: guest hypervisor can use NPT but this is not required.
It may use shadow paging. But an AMD cpu with NPT capability is
required since shadow-on-shadow is not supported.

 >  Unfortunately, on Intel it does not include EPT.
>
> There may be some other simulators that have EPT/NPT - I don't know.
>
> Cheers,
>
> Tim.


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