vfio iommu type1: Fix size argument to vfio_find_dma() in pin_pages/unpin_pages

Passing zero for the size to vfio_find_dma() isn't compatible with
matching the start address of an existing vfio_dma. Doing so triggers a
corner case. In vfio_find_dma(), when the start address is equal to
dma->iova and size is 0, check for the end of search range makes it to
take wrong side of RB-tree. That fails the search even though the address
is present in mapped dma ranges.
In functions pin_pages and unpin_pages, the iova which is being searched
is base address of page to be pinned or unpinned. So here size should be
set to PAGE_SIZE, as argument to vfio_find_dma().
Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
Signed-off-by: Neo Jia <cjia@nvidia.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

drivers/vfio/vfio_iommu_type1.c

@@ -581,7 +581,7 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
 		struct vfio_pfn *vpfn;
 
 		iova = user_pfn[i] << PAGE_SHIFT;
-		dma = vfio_find_dma(iommu, iova, 0);
+		dma = vfio_find_dma(iommu, iova, PAGE_SIZE);
 		if (!dma) {
 			ret = -EINVAL;
 			goto pin_unwind;
@@ -622,7 +622,7 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
 		dma_addr_t iova;
 
 		iova = user_pfn[j] << PAGE_SHIFT;
-		dma = vfio_find_dma(iommu, iova, 0);
+		dma = vfio_find_dma(iommu, iova, PAGE_SIZE);
 		vfio_unpin_page_external(dma, iova, do_accounting);
 		phys_pfn[j] = 0;
 	}
@@ -659,7 +659,7 @@ static int vfio_iommu_type1_unpin_pages(void *iommu_data,
 		dma_addr_t iova;
 
 		iova = user_pfn[i] << PAGE_SHIFT;
-		dma = vfio_find_dma(iommu, iova, 0);
+		dma = vfio_find_dma(iommu, iova, PAGE_SIZE);
 		if (!dma)
 			goto unpin_exit;
 		vfio_unpin_page_external(dma, iova, do_accounting);