Re: [PATCH RFC 15/19] iommu/arm-smmu-v3: Add set_dirty_tracking_range() support

Joao Martins
2022-04-29T11:05:46Z

On 4/29/22 09:28, Tian, Kevin wrote:
>> From: Joao Martins <joao.m.martins@oracle.com>
>> Sent: Friday, April 29, 2022 5:09 AM
>>
>> Similar to .read_and_clear_dirty() use the page table
>> walker helper functions and set DBM|RDONLY bit, thus
>> switching the IOPTE to writeable-clean.
>
> this should not be one-off if the operation needs to be
> applied to IOPTE. Say a map request comes right after
> set_dirty_tracking() is called. If it's agreed to remove
> the range op then smmu driver should record the tracking
> status internally and then apply the modifier to all the new
> mappings automatically before dirty tracking is disabled.
> Otherwise the same logic needs to be kept in iommufd to
> call set_dirty_tracking_range() explicitly for every new
> iopt_area created within the tracking window.

Gah, I totally missed that by mistake. New mappings aren't
carrying over the "DBM is set". This needs a new io-pgtable
quirk added post dirty-tracking toggling.

I can adjust, but I am at odds on including this in a future
iteration given that I can't really test any of this stuff.
Might drop the driver until I have hardware/emulation I can
use (or maybe others can take over this). It was included
for revising the iommu core ops and whether iommufd was
affected by it.

I'll delete the range op, and let smmu v3 driver walk its
own IO pgtables.