Re: [PATCH 14/14] iommufd/selftest: Add test to verify iommufd preservation

[Pranjal Shrivastava]

On Tue, Feb 03, 2026 at 10:09:48PM +0000, Samiullah Khawaja wrote:
> Test iommufd preservation by setting up an iommufd and vfio cdev and
> preserve it across live update. Test takes VFIO cdev path of a device
> bound to vfio-pci driver and binds it to an iommufd being preserved. It
> also preserves the vfio cdev so the iommufd state associated with it is
> also preserved.
> 
> The restore path is tested by restoring the preserved vfio cdev only.
> Test tries to finish the session without restoring iommufd and confirms
> that it fails.
> 
> Signed-off-by: Samiullah Khawaja <skhawaja@xxxxxxxxxx>
> Signed-off-by: YiFei Zhu <zhuyifei@xxxxxxxxxx>
> ---
>  tools/testing/selftests/iommu/Makefile        |  12 +
>  .../selftests/iommu/iommufd_liveupdate.c      | 209 ++++++++++++++++++
>  2 files changed, 221 insertions(+)
>  create mode 100644 tools/testing/selftests/iommu/iommufd_liveupdate.c
> 
> diff --git a/tools/testing/selftests/iommu/Makefile b/tools/testing/selftests/iommu/Makefile
> index 84abeb2f0949..263195af4d6a 100644
> --- a/tools/testing/selftests/iommu/Makefile
> +++ b/tools/testing/selftests/iommu/Makefile
> @@ -7,4 +7,16 @@ TEST_GEN_PROGS :=
>  TEST_GEN_PROGS += iommufd
>  TEST_GEN_PROGS += iommufd_fail_nth
>  
> +TEST_GEN_PROGS_EXTENDED += iommufd_liveupdate
> +
>  include ../lib.mk
> +include ../liveupdate/lib/libliveupdate.mk
> +
> +CFLAGS += -I$(top_srcdir)/tools/include
> +CFLAGS += -MD
> +CFLAGS += $(EXTRA_CFLAGS)
> +
> +$(TEST_GEN_PROGS_EXTENDED): %: %.o $(LIBLIVEUPDATE_O)
> +	$(CC) $(CFLAGS) $(CPPFLAGS) $(LDFLAGS) $(TARGET_ARCH) $< $(LIBLIVEUPDATE_O) $(LDLIBS) -static -o $@
> +
> +EXTRA_CLEAN += $(LIBLIVEUPDATE_O)
> diff --git a/tools/testing/selftests/iommu/iommufd_liveupdate.c b/tools/testing/selftests/iommu/iommufd_liveupdate.c
> new file mode 100644
> index 000000000000..8b4ea9f2b7e9
> --- /dev/null
> +++ b/tools/testing/selftests/iommu/iommufd_liveupdate.c
> @@ -0,0 +1,209 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +
> +/*
> + * Copyright (c) 2025, Google LLC.
> + * Samiullah Khawaja <skhawaja@xxxxxxxxxx>
> + */
> +
> +#include <fcntl.h>
> +#include <sys/ioctl.h>
> +#include <sys/mman.h>
> +#include <stdbool.h>
> +#include <unistd.h>
> +
> +#define __EXPORTED_HEADERS__
> +#include <linux/iommufd.h>
> +#include <linux/types.h>
> +#include <linux/vfio.h>
> +#include <linux/sizes.h>
> +#include <libliveupdate.h>
> +
> +#include "../kselftest.h"
> +
> +#define ksft_assert(condition) \
> +	do { if (!(condition)) \
> +	ksft_exit_fail_msg("Failed: %s at %s %d: %s\n", \
> +	#condition, __FILE__, __LINE__, strerror(errno)); } while (0)
> +
> +int setup_cdev(const char *vfio_cdev_path)
> +{
> +	int cdev_fd;
> +
> +	cdev_fd = open(vfio_cdev_path, O_RDWR);
> +	if (cdev_fd < 0)
> +		ksft_exit_skip("Failed to open VFIO cdev: %s\n", vfio_cdev_path);
> +
> +	return cdev_fd;
> +}
> +
> +int open_iommufd(void)
> +{
> +	int iommufd;
> +
> +	iommufd = open("/dev/iommu", O_RDWR);
> +	if (iommufd < 0)
> +		ksft_exit_skip("Failed to open /dev/iommu. IOMMUFD support not enabled.\n");
> +
> +	return iommufd;
> +}
> +
> +int setup_iommufd(int iommufd, int memfd, int cdev_fd, int hwpt_token)
> +{
> +	int ret;
> +
> +	struct vfio_device_bind_iommufd bind = {
> +		.argsz = sizeof(bind),
> +		.flags = 0,
> +	};
> +	struct iommu_ioas_alloc alloc_data = {
> +		.size = sizeof(alloc_data),
> +		.flags = 0,
> +	};
> +	struct iommu_hwpt_alloc hwpt_alloc = {
> +		.size = sizeof(hwpt_alloc),
> +		.flags = 0,
> +	};
> +	struct vfio_device_attach_iommufd_pt attach_data = {
> +		.argsz = sizeof(attach_data),
> +		.flags = 0,
> +	};
> +	struct iommu_hwpt_lu_set_preserve set_preserve = {
> +		.size = sizeof(set_preserve),
> +		.hwpt_token = hwpt_token,
> +	};
> +	struct iommu_ioas_map_file map_file = {
> +		.size = sizeof(map_file),
> +		.length = SZ_1M,
> +		.flags = IOMMU_IOAS_MAP_WRITEABLE | IOMMU_IOAS_MAP_READABLE,
> +		.iova = SZ_4G,
> +		.fd = memfd,
> +		.start = 0,
> +	};
> +
> +	bind.iommufd = iommufd;
> +	ret = ioctl(cdev_fd, VFIO_DEVICE_BIND_IOMMUFD, &bind);
> +	ksft_assert(!ret);
> +
> +	ret = ioctl(iommufd, IOMMU_IOAS_ALLOC, &alloc_data);
> +	ksft_assert(!ret);
> +
> +	hwpt_alloc.dev_id = bind.out_devid;
> +	hwpt_alloc.pt_id = alloc_data.out_ioas_id;
> +	ret = ioctl(iommufd, IOMMU_HWPT_ALLOC, &hwpt_alloc);
> +	ksft_assert(!ret);
> +
> +	attach_data.pt_id = hwpt_alloc.out_hwpt_id;
> +	ret = ioctl(cdev_fd, VFIO_DEVICE_ATTACH_IOMMUFD_PT, &attach_data);
> +	ksft_assert(!ret);
> +
> +	map_file.ioas_id = alloc_data.out_ioas_id;
> +	ret = ioctl(iommufd, IOMMU_IOAS_MAP_FILE, &map_file);
> +	ksft_assert(!ret);
> +
> +	set_preserve.hwpt_id = attach_data.pt_id;
> +	ret = ioctl(iommufd, IOMMU_HWPT_LU_SET_PRESERVE, &set_preserve);
> +	ksft_assert(!ret);
> +
> +	return ret;
> +}
> +
> +static int create_sealed_memfd(size_t size)
> +{
> +	int fd, ret;
> +
> +	fd = memfd_create("buffer", MFD_ALLOW_SEALING);
> +	ksft_assert(fd > 0);
> +
> +	ret = ftruncate(fd, size);
> +	ksft_assert(!ret);
> +
> +	ret = fcntl(fd, F_ADD_SEALS,
> +		    F_SEAL_GROW | F_SEAL_SHRINK | F_SEAL_SEAL);
> +	ksft_assert(!ret);
> +
> +	return fd;
> +}
> +
> +int main(int argc, char *argv[])

The iommufd selftest directory heavily utilizes the standard kselftest
harness (TEST_F, EXPECT_EQ, ASSERT_EQ), by writing a raw main(), this 
patch circumvents the standard test reporting structure (like returning 1
on argc < 2 instead of ksft_exit_skip(), and returning 0 at the end
instead of ksft_exit_pass() etc.). We should rewrite this cleanly 
following the existing iommufd test infrastructure using TEST_F blocks.

> +{
> +	int iommufd, cdev_fd, memfd, luo, session, ret;
> +	const int token = 0x123456;
> +	const int cdev_token = 0x654321;
> +	const int hwpt_token = 0x789012;
> +	const int memfd_token = 0x890123;

Shouldn't these be u64? Defining them as signed int-s undermines that
contract?

> +
> +	if (argc < 2) {
> +		printf("Usage: ./iommufd_liveupdate <vfio_cdev_path>\n");
> +		return 1;
> +	}
> +
> +	luo = luo_open_device();
> +	ksft_assert(luo > 0);
> +
> +	session = luo_retrieve_session(luo, "iommufd-test");

[ ---- >8 ---- ]

Thanks,
Praan