[PATCH 0/3] iommu: Avoid DMA ops domain refcount contention

On 17/08/18 08:24, Christoph Hellwig wrote:

I plan to make the arm iommu dma ops generic and move them to
drivers/iommu for the 4.20 merge window.

You mean 32-bit arm? The only place that code should move to is 
/dev/null ;) - the plan has always been to convert it to use groups and 
default domains so it can just plug iommu-dma in. The tricky bit is 
either weaning the users of the private arm_iommu_*() API onto generic 
IOMMU API usage, or at least implementing transitional wrappers in a way 
that doesn't break anything.

 Because of that it would
be great to create a stable branch or even pull this in through
the dma-mapping tree entirely.

FWIW I might still need to tweak the first patch depending on how we 
choose to resolve the interaction between DMA ops and unmanaged 
domains[1] - if we want to add fallback paths to iommu-dma instead of 
swizzling device ops then the assumptions for this hook change and it 
will need to reference group->domain rather than group->default_domain.

Robin.


[1] 
https://www.mail-archive.com/dri-devel at lists.freedesktop.org/msg230275.html