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

Marek Szyprowski
2025-07-08T15:57:40Z

On 08.07.2025 14:56, Marek Szyprowski wrote:
> On 08.07.2025 14:06, Leon Romanovsky wrote:
>> On Tue, Jul 08, 2025 at 01:45:20PM +0200, Marek Szyprowski wrote:
>>> 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.
>> Jerome is not active in HMM world for a long time already.
>> HMM tree is managed by us (RDMA)
>> https://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma.git/log/?h=hmm
>> ➜  kernel git:(m/dmabuf-vfio) git log --merges mm/hmm.c
>> ...
>> Pull HMM updates from Jason Gunthorpe:
>> ...
>>
>> https://web.git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=58ba80c4740212c29a1cf9b48f588e60a7612209
>>
>> +hmm        git
>> git://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma.git#hmm
>>
>> We just never bothered to reflect current situation in MAINTAINERS file.
>
> Maybe this is the time to update it :)
>
> I was just a bit confused that no-one commented the HMM patch, but if
> You maintain it, then this is okay.

I've applied the last patch to dma-mapping-for-next branch.

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