[PATCH 1/1] drm/i915: Drop user contexts on device remove

Chris Wilson chris at chris-wilson.co.uk
Fri Apr 24 14:15:35 UTC 2020

Quoting Chris Wilson (2020-04-24 15:09:27)
> Quoting Janusz Krzysztofik (2020-04-24 14:47:42)
> > Contexts associated with open file descriptors are now closed on file
> > close.  If a device is removed while being open, DMA API warns about
> > device associated mappings still active.  Moreover, subsequent removal
> > of contexts on device close may trigger a bug in intel-iommu code on
> > dma_unmap attempt.
> The contexts are not the primary association with dma-mappings. The
> objects are dma-mapped independently, what you are doing here is
> indirectly releasing the dma-mapping of the ppGTT page directory.
> While it seems to be only solving half the problem, automatically
> marking the vm as closed on driver_unregister sounds viable. But it
> feels like we should just be marking the device as going away and just
> ignore all the dma unmapping.
> We could do something like set up a dummy dma_map_ops in unregister,
> and so discard all the unmaps, report error for further maps, and leave
> in place until the next device replaces it. It appears that can be done
> with just a blank dma_map_ops. Seems cheeky, but it just might work...

I wonder if

void i915_driver_remove(struct drm_i915_private *i915)


+       set_dma_ops(&i915->drm.pdev->dev, &dma_dummy_ops);

is all we need.

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