[dpdk-dev] [PATCH 2/2] vfio: modify spapr iommu support to use static window sizing

[Burakov, Anatoly]

On 05-May-20 5:26 PM, David Christensen wrote:
>>>>>> That's not even mentioning the fact that the user may register 
>>>>>> external memory for DMA which may cause the window to be of 
>>>>>> insufficient size to cover said external memory.
> 
> Regarding external memory, I can think of two obvious options:
> 
> 1) Skip window sizing altogether if external memory is detected and 
> assume the user has set things up appropriately.

A third option is just to caution users that external memory might not 
work on PPC64, and rely on my patch and the DMA mask infrastructure to 
ensure that any IOVA user requests, we can satisfy. If they can't be, 
user can adjust their IOVA request accordingly.

> 2) Add an EAL command line option --iova-len that would allow the 
> external memory requirements to be considered it required.
> 

I'm not keen on an additional platform-specific EAL option, to be 
honest, and i don't think others would be either.

> I'll work on a new patch with (2) along with the other changes discussed 
> and resubmit.  Thanks for the feedback.
> 
> Dave


-- 
Thanks,
Anatoly