AMD IOMMU [PSARC/2008/561]

[Vikram Hegde]

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

Vikram


Matthew Jacob wrote:
> On 09/03/08 16:34, Jerry Gilliam wrote:
>> I am sponsoring the following fast-track for Vikram Hegde.  This
>> case presents an overview and architectural details on an IOMMU
>> for AMD cpus.  This information is being presented for information
>> only, for discussion and future reference.  As there's nothing to
>> approve, I believe Closed Approved Automatic is appropriate.
>>
>>
>>
>>   
>
> 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.