Re: [PATCH 2/2] vfio: selftests: Add iommufd multi iommu test

[David Matlack <dmatlack@google.com>]

On 2026-05-05 10:14 PM, Samiullah Khawaja wrote:
> Add a test for iommufd to verify creation of multiple iommus using an
> already setup iommufd and switch between them.
> 
> Signed-off-by: Samiullah Khawaja <skhawaja@google.com>
> ---
>  tools/testing/selftests/vfio/Makefile         |   1 +
>  .../vfio/vfio_iommufd_multi_iommu_test.c      | 203 ++++++++++++++++++
>  2 files changed, 204 insertions(+)
>  create mode 100644 tools/testing/selftests/vfio/vfio_iommufd_multi_iommu_test.c
> 
> diff --git a/tools/testing/selftests/vfio/Makefile b/tools/testing/selftests/vfio/Makefile
> index 0684932d91bf..24bdeaad590f 100644
> --- a/tools/testing/selftests/vfio/Makefile
> +++ b/tools/testing/selftests/vfio/Makefile
> @@ -8,6 +8,7 @@ else
>  CFLAGS = $(KHDR_INCLUDES)
>  TEST_GEN_PROGS += vfio_dma_mapping_test
>  TEST_GEN_PROGS += vfio_dma_mapping_mmio_test
> +TEST_GEN_PROGS += vfio_iommufd_multi_iommu_test
>  TEST_GEN_PROGS += vfio_iommufd_setup_test
>  TEST_GEN_PROGS += vfio_pci_device_test
>  TEST_GEN_PROGS += vfio_pci_device_init_perf_test
> diff --git a/tools/testing/selftests/vfio/vfio_iommufd_multi_iommu_test.c b/tools/testing/selftests/vfio/vfio_iommufd_multi_iommu_test.c
> new file mode 100644
> index 000000000000..7199c662637c
> --- /dev/null
> +++ b/tools/testing/selftests/vfio/vfio_iommufd_multi_iommu_test.c
> @@ -0,0 +1,203 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +#include <sys/ioctl.h>
> +#include <sys/mman.h>
> +
> +#include <linux/sizes.h>
> +#include <linux/vfio.h>
> +
> +#include <libvfio.h>
> +
> +#include "kselftest_harness.h"
> +
> +static const char *device_bdf;
> +
> +#define IOMMU_DEFAULT 0
> +#define IOMMU_WITH_PT 1
> +#define IOMMU_WITHOUT_PT 2
> +
> +static void region_setup(struct iommu *iommu,
> +			 struct iova_allocator *iova_allocator,
> +			 struct dma_region *region, u64 size)
> +{
> +	const int flags = MAP_SHARED | MAP_ANONYMOUS;
> +	const int prot = PROT_READ | PROT_WRITE;
> +	void *vaddr;
> +
> +	vaddr = mmap(NULL, size, prot, flags, -1, 0);
> +	VFIO_ASSERT_NE(vaddr, MAP_FAILED);
> +
> +	region->vaddr = vaddr;
> +	region->iova = iova_allocator_alloc(iova_allocator, size);
> +	region->size = size;
> +
> +	iommu_map(iommu, region);
> +}
> +
> +static void region_teardown(struct iommu *iommu, struct dma_region *region)
> +{
> +	iommu_unmap(iommu, region);
> +	VFIO_ASSERT_EQ(munmap(region->vaddr, region->size), 0);
> +}

Can you create library helpers in the library to share with
vfio_pci_driver_test.c?

  dma_region_setup()
  dma_region_teardown()

> +
> +FIXTURE(vfio_iommufd_multi_iommu_test) {
> +	struct iommu *iommu;
> +	struct vfio_pci_device *device;
> +	struct iova_allocator *iova_allocator;
> +	struct dma_region memcpy_region;
> +	void *vaddr;
> +
> +	u64 size;
> +	void *src;
> +	void *dst;
> +	iova_t src_iova;
> +	iova_t dst_iova;
> +};
> +
> +FIXTURE_SETUP(vfio_iommufd_multi_iommu_test)
> +{
> +	struct vfio_pci_driver *driver;
> +
> +	self->iommu = iommu_init("iommufd");

MODE_IOMMUFD

> +	self->device = vfio_pci_device_init(device_bdf, self->iommu);
> +	self->iova_allocator = iova_allocator_init(self->iommu);
> +
> +	driver = &self->device->driver;
> +
> +	region_setup(self->iommu, self->iova_allocator, &self->memcpy_region, SZ_1G);
> +	region_setup(self->iommu, self->iova_allocator, &driver->region, SZ_2M);
> +
> +	if (driver->ops)
> +		vfio_pci_driver_init(self->device);
> +
> +	self->size = self->memcpy_region.size / 2;
> +	self->src = self->memcpy_region.vaddr;
> +	self->dst = self->src + self->size;
> +
> +	self->src_iova = to_iova(self->device, self->src);
> +	self->dst_iova = to_iova(self->device, self->dst);
> +}
> +
> +FIXTURE_TEARDOWN(vfio_iommufd_multi_iommu_test)
> +{
> +	struct vfio_pci_driver *driver = &self->device->driver;
> +
> +	if (driver->ops)
> +		vfio_pci_driver_remove(self->device);
> +
> +	region_teardown(self->iommu, &self->memcpy_region);
> +	region_teardown(self->iommu, &driver->region);
> +
> +	iova_allocator_cleanup(self->iova_allocator);
> +	vfio_pci_device_cleanup(self->device);
> +	iommu_cleanup(self->iommu);
> +}
> +
> +FIXTURE_VARIANT(vfio_iommufd_multi_iommu_test) {
> +	u32 start_iommu;
> +	u32 end_iommu;
> +};
> +
> +#define ADD_IOMMU_VARIANT(S, E) \
> +	FIXTURE_VARIANT_ADD(vfio_iommufd_multi_iommu_test, S##_to_##E) { \
> +		.start_iommu = IOMMU_##S, \
> +		.end_iommu = IOMMU_##E \
> +	};
> +
> +#define ADD_ALL_VARIANTS(S) \
> +	ADD_IOMMU_VARIANT(S, DEFAULT) \
> +	ADD_IOMMU_VARIANT(S, WITH_PT) \
> +	ADD_IOMMU_VARIANT(S, WITHOUT_PT)
> +
> +ADD_ALL_VARIANTS(DEFAULT)
> +ADD_ALL_VARIANTS(WITH_PT)
> +ADD_ALL_VARIANTS(WITHOUT_PT)
> +
> +static struct iommu *setup_variant_iommu(struct iommu *fixture_iommu,
> +					 u32 dev_id, u32 type)
> +{
> +	switch (type) {
> +	case IOMMU_WITH_PT:
> +		return iommufd_iommu_init(fixture_iommu->iommufd, dev_id,
> +					  IOMMUFD_IOMMU_INIT_CREATE_PT);
> +	case IOMMU_WITHOUT_PT:
> +		return iommufd_iommu_init(fixture_iommu->iommufd, dev_id, 0);
> +	default:
> +		return fixture_iommu;
> +	}
> +}
> +
> +static void test_memcpy(struct vfio_pci_device *device, void *src, void *dst,
> +			iova_t src_iova, iova_t dst_iova, u64 size, char val)
> +{
> +	if (!device->driver.ops)
> +		return;
> +
> +	memset(src, val, size);
> +	memset(dst, 0, size);
> +
> +	vfio_pci_driver_memcpy_start(device, src_iova, dst_iova, size, 100);

Why do 100 copies?

> +	VFIO_ASSERT_EQ(vfio_pci_driver_memcpy_wait(device), 0);
> +	VFIO_ASSERT_EQ(memcmp(src, dst, size), 0);
> +}
> +
> +TEST_F(vfio_iommufd_multi_iommu_test, memcpy)
> +{
> +	struct dma_region memcpy_region1, driver_region1;
> +	struct dma_region memcpy_region2, driver_region2;
> +	struct iommu *iommu1;
> +	struct iommu *iommu2;
> +
> +	iommu1 = setup_variant_iommu(self->iommu, self->device->dev_id,
> +				     variant->start_iommu);
> +	if (iommu1 != self->iommu) {
> +		memcpy_region1 = self->memcpy_region;
> +		driver_region1 = self->device->driver.region;
> +
> +		iommu_map(iommu1, &memcpy_region1);

Can you make a helper to copy dma_region into a new iommu? It should set
up the new struct dma_region based on the old one, re-initialize the
link field, and then call iommu_map().

> +		iommu_map(iommu1, &driver_region1);
> +
> +		vfio_pci_device_attach_iommu(self->device, iommu1);
> +	}
> +
> +	test_memcpy(self->device, self->src, self->dst, self->src_iova,
> +		    self->dst_iova, self->size, 'x');

nit: You can pass in self to avoid unpacking it in every call to
test_memcpy(). The type would be:

  struct _test_data_vfio_iommufd_multi_iommu_test *self

> +
> +	iommu2 = setup_variant_iommu(self->iommu, self->device->dev_id,
> +				     variant->end_iommu);
> +	if (iommu2 != self->iommu) {
> +		memcpy_region2 = self->memcpy_region;
> +		driver_region2 = self->device->driver.region;
> +
> +		iommu_map(iommu2, &memcpy_region2);
> +		iommu_map(iommu2, &driver_region2);
> +	}
> +
> +	vfio_pci_device_attach_iommu(self->device, iommu2);
> +	test_memcpy(self->device, self->src, self->dst, self->src_iova,
> +		    self->dst_iova, self->size, 'a');

test_memcpy() zeroes self->dst every time so do you need to use a
different character for each call?

> +
> +	vfio_pci_device_attach_iommu(self->device, iommu1);
> +	test_memcpy(self->device, self->src, self->dst, self->src_iova,
> +		    self->dst_iova, self->size, '1');
> +
> +	if (iommu1 != self->iommu) {
> +		/* attach back to default iommu for cleanup */
> +		vfio_pci_device_attach_iommu(self->device, self->iommu);
> +		iommu_unmap(iommu1, &memcpy_region1);
> +		iommu_unmap(iommu1, &driver_region1);
> +		iommu_cleanup(iommu1);
> +	}
> +
> +	if (iommu2 != self->iommu) {
> +		iommu_unmap(iommu2, &memcpy_region2);
> +		iommu_unmap(iommu2, &driver_region2);

nit: You don't need to unmap before cleanup. Is this just to exercise
that unmap works on the variant iommus?

> +		iommu_cleanup(iommu2);
> +	}
> +}
> +
> +int main(int argc, char *argv[])
> +{
> +	device_bdf = vfio_selftests_get_bdf(&argc, argv);
> +
> +	return test_harness_run(argc, argv);
> +}
> -- 
> 2.54.0.545.g6539524ca2-goog
>