Re: [Xen-ia64-devel] VTD is coming

[Isaku Yamahata <yamahata@xxxxxxxxxxxxx>]

On Fri, May 11, 2007 at 09:19:45AM +0800, Xu, Anthony wrote:
> >You seems to be thinking about IPF specific implementation, right?
> >The x86 VT-d patches which was posted to xen-devel has separate
> >page table for VTD. I don't know its current development status, though.
> >Making it arch-generic, it might be reused.
> >
> 
> Even in ia32/xen, they are planning to merge these two tables.
> 
> If host processor is ia32e (64bit).
>       Processor page table and vtd page table have similar format.
>       That's reasonable and easy to merge these two page tables.
> 
> If host processor is ia32(32bit)
>       These two page tables can't merge.
>       Because P2M is used as shadow page table (which is accessed by hardware)
> when guest is in protect mode with paging disabled and processor page table 
> and  vtd page table are very different.
> 
> XEN will decide if it will use one page table or separate page tables at boot 
> process when it can find out the underlying processor type.

Do you mean nexted page table(NPT) by 'processor page table'?
ia32 VT-d code would be very specific to ia32 so that
it seems very difficult to have arch generic code.
It would be reasonable to go for ia64 specific VT-d implementation.

-- 
yamahata

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