iommu: Explicitly skip bus address marked segments in __iommu_map_sg()

In order to support PCI P2PDMA mappings with dma-iommu, explicitly skip
any segments marked with sg_dma_mark_bus_address() in __iommu_map_sg().

These segments should not be mapped into the IOVA and will be handled
separately in as subsequent patch for dma-iommu.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

Author: lsgunth

drivers/iommu/iommu.c

@@ -2457,13 +2457,17 @@ static ssize_t __iommu_map_sg(struct iommu_domain *domain, unsigned long iova,
 			len = 0;
 		}
 
+		if (sg_is_dma_bus_address(sg))
+			goto next;
+
 		if (len) {
 			len += sg->length;
 		} else {
 			len = sg->length;
 			start = s_phys;
 		}
 
+next:
 		if (++i < nents)
 			sg = sg_next(sg);
 	}