Re: [PATCH 0/8] dma-mapping: migrate to physical address-based API

Marek Szyprowski
2025-07-08T11:45:31Z

On 08.07.2025 13:00, Leon Romanovsky wrote:
> On Tue, Jul 08, 2025 at 12:27:09PM +0200, Marek Szyprowski wrote:
>> On 30.06.2025 15:38, Christoph Hellwig wrote:
>>> On Fri, Jun 27, 2025 at 08:02:13PM +0300, Leon Romanovsky wrote:
>>>>> Thanks for this rework! I assume that the next step is to add map_phys
>>>>> callback also to the dma_map_ops and teach various dma-mapping providers
>>>>> to use it to avoid more phys-to-page-to-phys conversions.
>>>> Probably Christoph will say yes, however I personally don't see any
>>>> benefit in this. Maybe I wrong here, but all existing .map_page()
>>>> implementation platforms don't support p2p anyway. They won't benefit
>>>> from this such conversion.
>>> I think that conversion should eventually happen, and rather sooner than
>>> later.
>> Agreed.
>>
>> Applied patches 1-7 to my dma-mapping-next branch. Let me know if one
>> needs a stable branch with it.
> Thanks a lot, I don't think that stable branch is needed. Realistically
> speaking, my VFIO DMA work won't be merged this cycle, We are in -rc5,
> it is complete rewrite from RFC version and touches pci-p2p code (to
> remove dependency on struct page) in addition to VFIO, so it will take
> time.
>
> Regarding, last patch (hmm), it will be great if you can take it.
> We didn't touch anything in hmm.c this cycle and have no plans to send PR.
> It can safely go through your tree.

Okay, then I would like to get an explicit ack from Jérôme for this.

>> Leon, it would be great if You could also prepare an incremental patch
>> adding map_phys callback to the dma_maps_ops, so the individual
>> arch-specific dma-mapping providers can be then converted (or simplified
>> in many cases) too.
> Sure, will do.

Thanks!

Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland