Re: [PATCH] mm/hmm: Allow hmm_dma_map_alloc() to tolerate NULL device

Daisuke Matsuda
2025-05-23T15:56:11Z

On 2025/05/24 0:42, Christoph Hellwig wrote:
> Thank you very much, but I know rxe very well. And given your apparent
> knowledge of the rdma subsystem you should also know pretty well that
> it does not otherwise call into the dma mapping core for virtual devices
> because calling into the dma mapping code is not valid for the virtual
> devices.
>
> Please fix the rdma core to not call into the hmm dma mapping helpers
> for the ib_uses_virt_dma() case.
>

Thank you for the clarification and guidance.

I'll look into updating the RDMA core to avoid calling hmm_dma_map_alloc() when ib_uses_virt_dma() is true. That should help keep the layering and responsibilities properly separated.

Thanks again,
Daisuke