AMD IOMMU [PSARC/2008/561]

[Matthew Jacob]

On 09/03/08 17:07, Vikram Hegde wrote:
> Hi,
>
>> Abilities to disable the IOMMU as a choice? Performance impact on 
>> various systems and interactions with other projects that have gone 
>> to some length to work within S/G and its performance 
>> characteristics. How will this affect them? Cache effects? 
>> Interactions with some VM work currently being undertaken?
>>
>> I can't imagine such a major change being closed/approved/automatic. 
> Performance is driver dependant. There is no way a single project team 
> can test the gamut of drivers out there and certify that the IOMMU 
> will  give acceptable performance for all needs (which is itself a 
> subjective opinion). 

No, it's a measurable value- not subjective.

> We have always planned to provide the ability to disable the IOMMU on 
> a per driver basis. Does that address your performance concerns ?
>

Yes, but as this is a spec in advance of actual implementation, could 
you make sure that 'plan' is on record?