Re: [PATCH] dma-debug: Skip cacheline tracking for MMIO mappings

[Marek Szyprowski <m.szyprowski@samsung.com>]

On 13.10.2026 14:43, Robin Murphy wrote:
> On 13/10/2026 12:44 pm, Leon Romanovsky wrote:
>> From: Leon Romanovsky <leonro@nvidia.com>
>>
>> Mapping one MMIO dma-buf for many RDMA importers overflows dma-debug's
>> cacheline overlap counter and triggers a warning. DMA_ATTR_MMIO mappings
>> must never be CPU-cacheable, so CPU cacheline overlap tracking does not
>> apply to them.
>>
>> Skip MMIO entries in both cacheline insertion and removal. Keep them in
>> the DMA entry hash so mapping and unmapping checks still run.
>
> Seems fair;
>
> Reviewed-by: Robin Murphy <robin.murphy@arm.com>
>
> [...]
>>
>> Fixes: 0e74b34dfc33 ("dma-debug: add support for resource mappings")
>
> Although it would be a challenge to backport _that_ far, so more realistically I'd probably say:
>
> Fixes: 3aa31a8bb11e ("dma-buf: provide phys_vec to scatter-gather mapping routine")
>
> since regular dma_map_resource() users are still never going to hit this making their one-off mapping of a UART FIFO or whatever.


Applied to dma-mapping-for-next with updated Fixes: tag, thanks!


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