Re: [PATCH V2 5/5] DO NOT MERGE: iommu: disable list appending in dma-iommu

[Christoph Hellwig]

On Thu, Sep 03, 2020 at 09:18:37PM +0100, Tom Murphy wrote:
> Disable combining sg segments in the dma-iommu api.
> Combining the sg segments exposes a bug in the intel i915 driver which
> causes visual artifacts and the screen to freeze. This is most likely
> because of how the i915 handles the returned list. It probably doesn't
> respect the returned value specifying the number of elements in the list
> and instead depends on the previous behaviour of the intel iommu driver
> which would return the same number of elements in the output list as in
> the input list.

So what is the state of addressing this properly in i915?  IF we can't
get it done ASAP I wonder if we need a runtime quirk to disable
merging instead of blocking this conversion..