Re: [PATCH RFC 07/12] iommufd: Data structure to provide IOVA to PFN mapping

[Jason Gunthorpe <jgg@nvidia.com>]

On Thu, Mar 24, 2022 at 03:09:46AM +0000, Tian, Kevin wrote:
> +		/*
> +		 * Can't cross areas that are not aligned to the system page
> +		 * size with this API.
> +		 */
> +		if (cur_iova % PAGE_SIZE) {
> +			rc = -EINVAL;
> +			goto out_remove;
> +		}
> 
> Currently it's done after iopt_pages_add_user() but before cur_iova 
> is adjusted, which implies the last add_user() will not be reverted in
> case of failed check here.

Oh, yes that's right too..

The above is wrong even, it didn't get fixed when page_offset was
done.

So more like this:

diff --git a/drivers/iommu/iommufd/io_pagetable.c b/drivers/iommu/iommufd/io_pagetable.c
index 1c08ae9b848fcf..9505f119df982e 100644
--- a/drivers/iommu/iommufd/io_pagetable.c
+++ b/drivers/iommu/iommufd/io_pagetable.c
@@ -23,7 +23,7 @@ static unsigned long iopt_area_iova_to_index(struct iopt_area *area,
 	if (IS_ENABLED(CONFIG_IOMMUFD_TEST))
 		WARN_ON(iova < iopt_area_iova(area) ||
 			iova > iopt_area_last_iova(area));
-	return (iova - (iopt_area_iova(area) & PAGE_MASK)) / PAGE_SIZE;
+	return (iova - (iopt_area_iova(area) - area->page_offset)) / PAGE_SIZE;
 }
 
 static struct iopt_area *iopt_find_exact_area(struct io_pagetable *iopt,
@@ -436,31 +436,45 @@ int iopt_access_pages(struct io_pagetable *iopt, unsigned long iova,
 		unsigned long index;
 
 		/* Need contiguous areas in the access */
-		if (iopt_area_iova(area) < cur_iova || !area->pages) {
+		if (iopt_area_iova(area) > cur_iova || !area->pages) {
 			rc = -EINVAL;
 			goto out_remove;
 		}
 
 		index = iopt_area_iova_to_index(area, cur_iova);
 		last_index = iopt_area_iova_to_index(area, last);
+
+		/*
+		 * The API can only return aligned pages, so the starting point
+		 * must be at a page boundary.
+		 */
+		if ((cur_iova - (iopt_area_iova(area) - area->page_offset)) %
+		    PAGE_SIZE) {
+			rc = -EINVAL;
+			goto out_remove;
+		}
+
+		/*
+		 * and an interior ending point must be at a page boundary
+		 */
+		if (last != last_iova &&
+		    (iopt_area_last_iova(area) - cur_iova + 1) % PAGE_SIZE) {
+			rc = -EINVAL;
+			goto out_remove;
+		}
+
 		rc = iopt_pages_add_user(area->pages, index, last_index,
 					 out_pages, write);
 		if (rc)
 			goto out_remove;
 		if (last == last_iova)
 			break;
-		/*
-		 * Can't cross areas that are not aligned to the system page
-		 * size with this API.
-		 */
-		if (cur_iova % PAGE_SIZE) {
-			rc = -EINVAL;
-			goto out_remove;
-		}
 		cur_iova = last + 1;
 		out_pages += last_index - index;
 		atomic_inc(&area->num_users);
 	}
+	if (cur_iova != last_iova)
+		goto out_remove;
 
 	up_read(&iopt->iova_rwsem);
 	return 0;
diff --git a/tools/testing/selftests/iommu/iommufd.c b/tools/testing/selftests/iommu/iommufd.c
index 5c47d706ed9449..a46e0f0ae82553 100644
--- a/tools/testing/selftests/iommu/iommufd.c
+++ b/tools/testing/selftests/iommu/iommufd.c
@@ -1221,5 +1221,6 @@ TEST_F(vfio_compat_mock_domain, get_info)
 /* FIXME test VFIO_IOMMU_MAP_DMA */
 /* FIXME test VFIO_IOMMU_UNMAP_DMA */
 /* FIXME test 2k iova alignment */
+/* FIXME cover boundary cases for iopt_access_pages()  */
 
 TEST_HARNESS_MAIN