drm/i915: Fix DMA mapped scatterlist walks
When walking DMA mapped scatterlists sg_dma_len has to be used since it can be different (coalesced) from the backing store entry. This also means we have to end the walk when encountering a zero length DMA entry and cannot rely on the normal sg list end marker. Both issues were there in theory for some time but were hidden by the fact Intel IOMMU driver was never coalescing entries. As there are ongoing efforts to change this we need to start handling it. v2: * Use unsigned int for local storing sg_dma_len. (Logan) Signed-off-by:Tvrtko Ursulin <tvrtko.ursulin@intel.com> References: 85d1225e ("drm/i915: Introduce & use new lightweight SGL iterators") References: b31144c0 ("drm/i915: Micro-optimise gen6_ppgtt_insert_entries()") Reported-by:
Tom Murphy <murphyt7@tcd.ie> Suggested-by: Tom Murphy <murphyt7@tcd.ie> # __sgt_iter Suggested-by: Logan Gunthorpe <logang@deltatee.com> # __sgt_iter Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> Cc: Chris Wilson <chris@chris-wilson.co.uk> Cc: Matthew Auld <matthew.auld@intel.com> Cc: Lu Baolu <baolu.lu@linux.intel.com> Reviewed-by:
Logan Gunthorpe <logang@deltatee.com> Link: https://patchwork.freedesktop.org/patch/msgid/20201006092508.1064287-1-tvrtko.ursulin@linux.intel.com
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