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

Samiullah Khawaja
2026-02-03T22:10:13Z

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@google.com>
Signed-off-by: YiFei Zhu <zhuyifei@google.com>
---
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@google.com>
+ */
+
+#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[])
+{
+ 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;
+
+ 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");
+ if (session == -ENOENT) {
+ session = luo_create_session(luo, "iommufd-test");
+
+ iommufd = open_iommufd();
+ memfd = create_sealed_memfd(SZ_1M);
+ cdev_fd = setup_cdev(argv[1]);
+
+ ret = setup_iommufd(iommufd, memfd, cdev_fd, hwpt_token);
+ ksft_assert(!ret);
+
+ /* Cannot preserve cdev without iommufd */
+ ret = luo_session_preserve_fd(session, cdev_fd, cdev_token);
+ ksft_assert(ret);
+
+ /* Cannot preserve iommufd without preserving memfd. */
+ ret = luo_session_preserve_fd(session, iommufd, token);
+ ksft_assert(ret);
+
+ ret = luo_session_preserve_fd(session, memfd, memfd_token);
+ ksft_assert(!ret);
+
+ ret = luo_session_preserve_fd(session, iommufd, token);
+ ksft_assert(!ret);
+
+ ret = luo_session_preserve_fd(session, cdev_fd, cdev_token);
+ ksft_assert(!ret);
+
+ close(session);
+ session = luo_create_session(luo, "iommufd-test");
+
+ ret = luo_session_preserve_fd(session, memfd, memfd_token);
+ ksft_assert(!ret);
+
+ ret = luo_session_preserve_fd(session, iommufd, token);
+ ksft_assert(!ret);
+
+ ret = luo_session_preserve_fd(session, cdev_fd, cdev_token);
+ ksft_assert(!ret);
+
+ daemonize_and_wait();
+ } else {
+ struct vfio_device_bind_iommufd bind = {
+ .argsz = sizeof(bind),
+ .flags = 0,
+ };
+
+ cdev_fd = luo_session_retrieve_fd(session, cdev_token);
+ ksft_assert(cdev_fd > 0);
+
+ iommufd = luo_session_retrieve_fd(session, token);
+ ksft_assert(iommufd < 0);
+
+ iommufd = open_iommufd();
+
+ bind.iommufd = iommufd;
+ ret = ioctl(cdev_fd, VFIO_DEVICE_BIND_IOMMUFD, &bind);
+ ksft_assert(ret);
+ ksft_assert(errno == EPERM);
+
+ /* Should fail */
+ ret = luo_session_finish(session);
+ ksft_assert(ret);
+ }
+
+ return 0;
+}
--
2.53.0.rc2.204.g2597b5adb4-goog