vfio_dma_mapping_test and vfio_pci_driver_test currently use iova=vaddr
as part of DMA mapping operations. The assumption that these IOVAs
are legal has held up on all the hardware we've tested so far, but is
not guaranteed. Make the tests more robust by using iova_allocator to
vend IOVAs, which queries legally accessible IOVAs from the underlying
IOMMUFD or VFIO container.

Signed-off-by: Alex Mastro <amastro@fb.com>
---
 tools/testing/selftests/vfio/vfio_dma_mapping_test.c |  5 ++++-
 tools/testing/selftests/vfio/vfio_pci_driver_test.c  | 12 ++++++++----
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/vfio/vfio_dma_mapping_test.c b/tools/testing/selftests/vfio/vfio_dma_mapping_test.c
index e1374aab96bd..102603d4407d 100644
--- a/tools/testing/selftests/vfio/vfio_dma_mapping_test.c
+++ b/tools/testing/selftests/vfio/vfio_dma_mapping_test.c
@@ -95,6 +95,7 @@ static int iommu_mapping_get(const char *bdf, u64 iova,
 
 FIXTURE(vfio_dma_mapping_test) {
 	struct vfio_pci_device *device;
+	struct iova_allocator *iova_allocator;
 };
 
 FIXTURE_VARIANT(vfio_dma_mapping_test) {
@@ -119,10 +120,12 @@ FIXTURE_VARIANT_ADD_ALL_IOMMU_MODES(anonymous_hugetlb_1gb, SZ_1G, MAP_HUGETLB |
 FIXTURE_SETUP(vfio_dma_mapping_test)
 {
 	self->device = vfio_pci_device_init(device_bdf, variant->iommu_mode);
+	self->iova_allocator = iova_allocator_init(self->device);
 }
 
 FIXTURE_TEARDOWN(vfio_dma_mapping_test)
 {
+	iova_allocator_cleanup(self->iova_allocator);
 	vfio_pci_device_cleanup(self->device);
 }
 
@@ -144,7 +147,7 @@ TEST_F(vfio_dma_mapping_test, dma_map_unmap)
 	else
 		ASSERT_NE(region.vaddr, MAP_FAILED);
 
-	region.iova = (u64)region.vaddr;
+	region.iova = iova_allocator_alloc(self->iova_allocator, size);
 	region.size = size;
 
 	vfio_pci_dma_map(self->device, &region);
diff --git a/tools/testing/selftests/vfio/vfio_pci_driver_test.c b/tools/testing/selftests/vfio/vfio_pci_driver_test.c
index 2dbd70b7db62..f69eec8b928d 100644
--- a/tools/testing/selftests/vfio/vfio_pci_driver_test.c
+++ b/tools/testing/selftests/vfio/vfio_pci_driver_test.c
@@ -19,6 +19,7 @@ static const char *device_bdf;
 } while (0)
 
 static void region_setup(struct vfio_pci_device *device,
+			 struct iova_allocator *iova_allocator,
 			 struct vfio_dma_region *region, u64 size)
 {
 	const int flags = MAP_SHARED | MAP_ANONYMOUS;
@@ -29,7 +30,7 @@ static void region_setup(struct vfio_pci_device *device,
 	VFIO_ASSERT_NE(vaddr, MAP_FAILED);
 
 	region->vaddr = vaddr;
-	region->iova = (u64)vaddr;
+	region->iova = iova_allocator_alloc(iova_allocator, size);
 	region->size = size;
 
 	vfio_pci_dma_map(device, region);
@@ -44,6 +45,7 @@ static void region_teardown(struct vfio_pci_device *device,
 
 FIXTURE(vfio_pci_driver_test) {
 	struct vfio_pci_device *device;
+	struct iova_allocator *iova_allocator;
 	struct vfio_dma_region memcpy_region;
 	void *vaddr;
 	int msi_fd;
@@ -72,14 +74,15 @@ FIXTURE_SETUP(vfio_pci_driver_test)
 	struct vfio_pci_driver *driver;
 
 	self->device = vfio_pci_device_init(device_bdf, variant->iommu_mode);
+	self->iova_allocator = iova_allocator_init(self->device);
 
 	driver = &self->device->driver;
 
-	region_setup(self->device, &self->memcpy_region, SZ_1G);
-	region_setup(self->device, &driver->region, SZ_2M);
+	region_setup(self->device, self->iova_allocator, &self->memcpy_region, SZ_1G);
+	region_setup(self->device, self->iova_allocator, &driver->region, SZ_2M);
 
 	/* Any IOVA that doesn't overlap memcpy_region and driver->region. */
-	self->unmapped_iova = 8UL * SZ_1G;
+	self->unmapped_iova = iova_allocator_alloc(self->iova_allocator, SZ_1G);
 
 	vfio_pci_driver_init(self->device);
 	self->msi_fd = self->device->msi_eventfds[driver->msi];
@@ -108,6 +111,7 @@ FIXTURE_TEARDOWN(vfio_pci_driver_test)
 	region_teardown(self->device, &self->memcpy_region);
 	region_teardown(self->device, &driver->region);
 
+	iova_allocator_cleanup(self->iova_allocator);
 	vfio_pci_device_cleanup(self->device);
 }
 

-- 
2.47.3

On Tue, 11 Nov 2025 06:52:05 -0800
Alex Mastro <amastro@fb.com> wrote:

> vfio_dma_mapping_test and vfio_pci_driver_test currently use iova=vaddr
> as part of DMA mapping operations. The assumption that these IOVAs
> are legal has held up on all the hardware we've tested so far, but is
> not guaranteed. Make the tests more robust by using iova_allocator to
> vend IOVAs, which queries legally accessible IOVAs from the underlying
> IOMMUFD or VFIO container.

I've reported hardware that it doesn't work on, QEMU emulates such
hardware.  The commit message suggests this is more of a theoretical
problem.  Thanks,

Alex

On Tue, Nov 11, 2025 at 10:09:37AM -0700, Alex Williamson wrote:
> On Tue, 11 Nov 2025 06:52:05 -0800
> Alex Mastro <amastro@fb.com> wrote:
> 
> > vfio_dma_mapping_test and vfio_pci_driver_test currently use iova=vaddr
> > as part of DMA mapping operations. The assumption that these IOVAs
> > are legal has held up on all the hardware we've tested so far, but is
> > not guaranteed. Make the tests more robust by using iova_allocator to
> > vend IOVAs, which queries legally accessible IOVAs from the underlying
> > IOMMUFD or VFIO container.
> 
> I've reported hardware that it doesn't work on, QEMU emulates such
> hardware.  The commit message suggests this is more of a theoretical
> problem.  Thanks,

Agree that it's misleading. I'll update the commit message to describe the
things you described earlier.