[Xen-devel] Re: about fixup_page_fault

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 17/12/2008 10:53, "Tim Deegan" <Tim.Deegan@xxxxxxxxxx> wrote:

> At 09:04 +0000 on 17 Dec (1229504644), Keir Fraser wrote:
>> A Xen fault shouldn't cause a lookup in guest tables for HVM guests.
> 
> Looks like it does, though. :(  The check in fixup_page_fault should
> probably be more like:

But wouldn't this just cause an infinite loop? Since shadow code would fix
up the fault in the guest shadow tables, which the hypervisor is not running
on?

 -- Keir

> if ( (paging_mode_external(d) && guest_mode(regs))
>      || (paging_mode_enabled(d) && !paging_mode_external(d)) )
> 
> That is, unconditionally call paging_fault() for PV guests (who
> shouldn't be allowed map the 0 page, right?), and call for HVM guests
> only if the guest caused the fault.
> 
> Potentially it can all be tidied up a bit by moving the other
> HVM-specific call out of the if (IN_HYPERVISOR_RANGE) block at the top.



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