[dpdk-dev] [PATCH v2 2/3] vfio: fix DMA mapping granularity for type1 iova as va

[Burakov, Anatoly]

On 05-Nov-20 9:04 AM, Nithin Dabilpuram wrote:
> Partial unmapping is not supported for VFIO IOMMU type1
> by kernel. Though kernel gives return as zero, the unmapped size
> returned will not be same as expected. So check for
> returned unmap size and return error.
> 
> For IOVA as PA, DMA mapping is already at memseg size
> granularity. Do the same even for IOVA as VA mode as
> DMA map/unmap triggered by heap allocations,
> maintain granularity of memseg page size so that heap
> expansion and contraction does not have this issue.
> 
> For user requested DMA map/unmap disallow partial unmapping
> for VFIO type1.
> 
> Fixes: 73a639085938 ("vfio: allow to map other memory regions")
> Cc: anatoly.burakov at intel.com
> Cc: stable at dpdk.org
> 
> Signed-off-by: Nithin Dabilpuram <ndabilpuram at marvell.com>
> ---

Maybe i just didn't have enough coffee today, but i still don't see why 
this "partial unmap" thing exists.

We are already mapping the addresses page-by-page, so surely "partial" 
unmaps can't even exist in the first place?

-- 
Thanks,
Anatoly