Xen devel - Sep 2008 - [PATCH] [VTD] Enable pass-through translation for Dom0

If pass-through field in extended capability register is set, set
pass-through translation type for Dom0, that means DMA requests with
Untranslated addresses are
processed as pass-through in Dom0, needn''t translate DMA requests
through a multi-level page-table.

Signed-off-by: Anthony Xu <anthony.xu@intel.com>
Signed-off-by: Weidong Han <weidong.han@intel.com>


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Taking security into accout, it''s not suitable to enable pass-through
translation for Dom0 by default when the pass-through field in extended
capability register is set. This feature is for people/usages who are
not overly worried about security/isolation, but want best performance.
With Dom0 use of pass-through, it reduces the IOTLB pressure for other
devices assigned to guest domains. 

Keir, 

Is it possible to add a command line option to control whether this is
enabled? 

Randy (Weidong)


Han, Weidong wrote:
> If pass-through field in extended capability register is set, set
> pass-through translation type for Dom0, that means DMA requests with
> Untranslated addresses are
> processed as pass-through in Dom0, needn''t translate DMA requests
> through a multi-level page-table.
> 
> Signed-off-by: Anthony Xu <anthony.xu@intel.com>
> Signed-off-by: Weidong Han <weidong.han@intel.com>

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