iommu: Switch gather->end to the inclusive end

Currently gather->end is "unsigned long" which may be overflow in
arch32 in the corner case: 0xfff00000 + 0x100000(iova + size).
Although it doesn't affect the size(end - start), it affects the checking
"gather->end < end"

This patch changes this "end" to the real end address
(end = start + size - 1). Correspondingly, update the length to
"end - start + 1".

Fixes: a7d20dc19d ("iommu: Introduce struct iommu_iotlb_gather for batching TLB flushes")
Signed-off-by: Yong Wu <yong.wu@mediatek.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210107122909.16317-5-yong.wu@mediatek.com
Signed-off-by: Will Deacon <will@kernel.org>

drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c

@@ -2280,7 +2280,7 @@ static void arm_smmu_iotlb_sync(struct iommu_domain *domain,
 {
 	struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
 
-	arm_smmu_tlb_inv_range(gather->start, gather->end - gather->start,
+	arm_smmu_tlb_inv_range(gather->start, gather->end - gather->start + 1,
 			       gather->pgsize, true, smmu_domain);
 }
 

drivers/iommu/mtk_iommu.c

@@ -443,7 +443,7 @@ static void mtk_iommu_iotlb_sync(struct iommu_domain *domain,
 				 struct iommu_iotlb_gather *gather)
 {
 	struct mtk_iommu_data *data = mtk_iommu_get_m4u_data();
-	size_t length = gather->end - gather->start;
+	size_t length = gather->end - gather->start + 1;
 
 	if (gather->start == ULONG_MAX)
 		return;

drivers/iommu/tegra-gart.c

@@ -270,7 +270,7 @@ static void gart_iommu_sync_map(struct iommu_domain *domain, unsigned long iova,
 static void gart_iommu_sync(struct iommu_domain *domain,
 			    struct iommu_iotlb_gather *gather)
 {
-	size_t length = gather->end - gather->start;
+	size_t length = gather->end - gather->start + 1;
 
 	gart_iommu_sync_map(domain, gather->start, length);
 }

include/linux/iommu.h

@@ -170,7 +170,7 @@ enum iommu_dev_features {
  * struct iommu_iotlb_gather - Range information for a pending IOTLB flush
  *
  * @start: IOVA representing the start of the range to be flushed
- * @end: IOVA representing the end of the range to be flushed (exclusive)
+ * @end: IOVA representing the end of the range to be flushed (inclusive)
  * @pgsize: The interval at which to perform the flush
  *
  * This structure is intended to be updated by multiple calls to the
@@ -539,7 +539,7 @@ static inline void iommu_iotlb_gather_add_page(struct iommu_domain *domain,
 					       struct iommu_iotlb_gather *gather,
 					       unsigned long iova, size_t size)
 {
-	unsigned long start = iova, end = start + size;
+	unsigned long start = iova, end = start + size - 1;
 
 	/*
 	 * If the new page is disjoint from the current range or is mapped at