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

["Burakov, Anatoly" <anatoly.burakov@intel.com>]

On 10-Nov-20 2:04 PM, Burakov, Anatoly wrote:
> 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@intel.com
>> Cc: stable@dpdk.org
>>
>> Signed-off-by: Nithin Dabilpuram <ndabilpuram@marvell.com>
>> ---
> 
> Maybe i just didn't have enough coffee today, but i still don't see why 
> this "partial unmap" thing exists.

Oh, right, this is for *user* mapped memory. Disregard this email.

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


-- 
Thanks,
Anatoly