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

["Han, Weidong" <weidong.han@xxxxxxxxx>]

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