IOMMU fixes for Linux v4.15-rc3

* Fix VT-d handling of scatterlists where sg->offset exceeds PAGE_SIZE
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Merge tag 'iommu-v4.15-rc3' of git://github.com/awilliam/linux-vfio

Pull IOMMU fix from Alex Williamson:
 "Fix VT-d handling of scatterlists where sg->offset exceeds PAGE_SIZE"

* tag 'iommu-v4.15-rc3' of git://github.com/awilliam/linux-vfio:
  iommu/vt-d: Fix scatterlist offset handling

drivers/iommu/intel-iommu.c

@@ -2250,10 +2250,12 @@ static int __domain_mapping(struct dmar_domain *domain, unsigned long iov_pfn,
 		uint64_t tmp;
 
 		if (!sg_res) {
+			unsigned int pgoff = sg->offset & ~PAGE_MASK;
+
 			sg_res = aligned_nrpages(sg->offset, sg->length);
-			sg->dma_address = ((dma_addr_t)iov_pfn << VTD_PAGE_SHIFT) + sg->offset;
+			sg->dma_address = ((dma_addr_t)iov_pfn << VTD_PAGE_SHIFT) + pgoff;
 			sg->dma_length = sg->length;
-			pteval = page_to_phys(sg_page(sg)) | prot;
+			pteval = (sg_phys(sg) - pgoff) | prot;
 			phys_pfn = pteval >> VTD_PAGE_SHIFT;
 		}
 
@@ -3787,7 +3789,7 @@ static int intel_nontranslate_map_sg(struct device *hddev,
 
 	for_each_sg(sglist, sg, nelems, i) {
 		BUG_ON(!sg_page(sg));
-		sg->dma_address = page_to_phys(sg_page(sg)) + sg->offset;
+		sg->dma_address = sg_phys(sg);
 		sg->dma_length = sg->length;
 	}
 	return nelems;