intel-iommu sg chaining support

x86_64 defines ARCH_HAS_SG_CHAIN. So if IOMMU implementations don't
support sg chaining, we will get data corruption.
Signed-off-by: NFUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Acked-by: NAnil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/pci/intel-iommu.c

@@ -1963,7 +1963,7 @@ static void intel_free_coherent(struct device *hwdev, size_t size,
 }
 
 #define SG_ENT_VIRT_ADDRESS(sg)	(page_address((sg)->page) + (sg)->offset)
-static void intel_unmap_sg(struct device *hwdev, struct scatterlist *sg,
+static void intel_unmap_sg(struct device *hwdev, struct scatterlist *sglist,
 	int nelems, int dir)
 {
 	int i;
@@ -1973,16 +1973,17 @@ static void intel_unmap_sg(struct device *hwdev, struct scatterlist *sg,
 	struct iova *iova;
 	size_t size = 0;
 	void *addr;
+	struct scatterlist *sg;
 
 	if (pdev->dev.archdata.iommu == DUMMY_DEVICE_DOMAIN_INFO)
 		return;
 
 	domain = find_domain(pdev);
 
-	iova = find_iova(&domain->iovad, IOVA_PFN(sg[0].dma_address));
+	iova = find_iova(&domain->iovad, IOVA_PFN(sglist[0].dma_address));
 	if (!iova)
 		return;
-	for (i = 0; i < nelems; i++, sg++) {
+	for_each_sg(sglist, sg, nelems, i) {
 		addr = SG_ENT_VIRT_ADDRESS(sg);
 		size += aligned_size((u64)addr, sg->length);
 	}
@@ -2003,21 +2004,21 @@ static void intel_unmap_sg(struct device *hwdev, struct scatterlist *sg,
 }
 
 static int intel_nontranslate_map_sg(struct device *hddev,
-	struct scatterlist *sg, int nelems, int dir)
+	struct scatterlist *sglist, int nelems, int dir)
 {
 	int i;
+	struct scatterlist *sg;
 
-	for (i = 0; i < nelems; i++) {
-		struct scatterlist *s = &sg[i];
-		BUG_ON(!s->page);
-		s->dma_address = virt_to_bus(SG_ENT_VIRT_ADDRESS(s));
-		s->dma_length = s->length;
+	for_each_sg(sglist, sg, nelems, i) {
+		BUG_ON(!sg->page);
+		sg->dma_address = virt_to_bus(SG_ENT_VIRT_ADDRESS(sg));
+		sg->dma_length = sg->length;
 	}
 	return nelems;
 }
 
-static int intel_map_sg(struct device *hwdev, struct scatterlist *sg,
-	int nelems, int dir)
+static int intel_map_sg(struct device *hwdev, struct scatterlist *sglist,
+				int nelems, int dir)
 {
 	void *addr;
 	int i;
@@ -2028,18 +2029,18 @@ static int intel_map_sg(struct device *hwdev, struct scatterlist *sg,
 	size_t offset = 0;
 	struct iova *iova = NULL;
 	int ret;
-	struct scatterlist *orig_sg = sg;
+	struct scatterlist *sg;
 	unsigned long start_addr;
 
 	BUG_ON(dir == DMA_NONE);
 	if (pdev->dev.archdata.iommu == DUMMY_DEVICE_DOMAIN_INFO)
-		return intel_nontranslate_map_sg(hwdev, sg, nelems, dir);
+		return intel_nontranslate_map_sg(hwdev, sglist, nelems, dir);
 
 	domain = get_valid_domain_for_dev(pdev);
 	if (!domain)
 		return 0;
 
-	for (i = 0; i < nelems; i++, sg++) {
+	for_each_sg(sglist, sg, nelems, i) {
 		addr = SG_ENT_VIRT_ADDRESS(sg);
 		addr = (void *)virt_to_phys(addr);
 		size += aligned_size((u64)addr, sg->length);
@@ -2047,7 +2048,7 @@ static int intel_map_sg(struct device *hwdev, struct scatterlist *sg,
 
 	iova = __intel_alloc_iova(hwdev, domain, size);
 	if (!iova) {
-		orig_sg->dma_length = 0;
+		sglist->dma_length = 0;
 		return 0;
 	}
 
@@ -2063,8 +2064,7 @@ static int intel_map_sg(struct device *hwdev, struct scatterlist *sg,
 
 	start_addr = iova->pfn_lo << PAGE_SHIFT_4K;
 	offset = 0;
-	sg = orig_sg;
-	for (i = 0; i < nelems; i++, sg++) {
+	for_each_sg(sglist, sg, nelems, i) {
 		addr = SG_ENT_VIRT_ADDRESS(sg);
 		addr = (void *)virt_to_phys(addr);
 		size = aligned_size((u64)addr, sg->length);