Re: [PATCH 2/6] system/physmem: IOMMU: Invoke the translate_size function if it is implemented

[Peter Xu]

On Thu, Oct 26, 2023 at 02:48:14PM +0800, Ethan Chen wrote:
> My target is to support IOPMP partially hit error. IOPMP checks whole memory 
> access region is in the same entry. If not, reject the access instead of 
> modify
> the access size.

Could you elaborate why is that important?  In what use case?

Consider IOVA mapped for address range iova=[0, 4K] only, here we have a
DMA request with range=[0, 8K].  Now my understanding is what you want to
achieve is don't trigger the DMA to [0, 4K] and fail the whole [0, 8K]
request.

Can we just fail at the latter DMA [4K, 8K] when it happens?  After all,
IIUC a device can split the 0-8K DMA into two smaller DMAs, then the 1st
chunk can succeed then if it falls in 0-4K.  Some further explanation of
the failure use case could be helpful.

Thanks,

-- 
Peter Xu