RE: [Xen-devel] [PATCH] [VTD] Separate VT-d page table from P2M table

["Ian Pratt" <Ian.Pratt@xxxxxxxxxxxxx>]

> If EPT supports 2MB page, we need separate VT-d table to let them work
> together. 

Are you saying that the VT-d 2MB page format is different from the EPT
2MB page format? Or that VTd does not support 2MB pages?

Ian

> What's more, sharing makes coupling between VT-d page table
> and p2m table. In case VT-d spec changes or p2m structure changes,
> shared table will be broken.

> Randy (Weidong)
> 
> Keir Fraser wrote:
> > What are the tradeoffs? One obvious tradeoff is that separate tables
> > doubles the memory overhead. What are the advantages of separate
> > tables? I believe currently we share the pagetables (right?). If so,
> > why would we even consider moving to separate tables?
> >
> >  -- Keir
> >
> > On 22/4/08 10:34, "Han, Weidong" <weidong.han@xxxxxxxxx> wrote:
> >
> >> Separate VT-d page table is by default. Shared VT-d page table may
> be
> >> easy and good in some cases. So we let them co-exist now. If shared
> >> VT-d page table is not necessary and useless, we can remove it
> >> easily in future.
> >>
> >> Randy (weidong)
> >>
> >> Keir Fraser wrote:
> >>> On 22/4/08 09:36, "Han, Weidong" <weidong.han@xxxxxxxxx> wrote:
> >>>
> >>>> Currently VT-d page table shares with P2M table, this patch
> >>>> supports separate VT-d page table. 1) add an option (vtd_share)
to
> >>>> control whether VT-d page table shares with P2M table or not.
> >>>
> >>> Why? Is this just another option that noone will understand.
> >>>
> >>>  -- Keir
> 
> 
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