[PATCH 2/2] selftests: iommu: skip when the mock device is not there

[Eva Kurchatova <eva.kurchatova@virtuozzo.com>]

Both iommufd tests need the mock device the iommufd module registers
under CONFIG_IOMMUFD_TEST, and they open /dev/iommu in every fixture
without checking, so on a kernel that does not provide it every case
fails on the open.

Checking the open is not enough on its own. /dev/iommu appears as soon
as the iommufd module is loaded, which says nothing about the mock
device: the release config here is CONFIG_IOMMUFD=m with
CONFIG_IOMMUFD_TEST unset, so the open succeeds and the tests fail later
in the ioctls that drive the mock device instead. Only the debug config
sets CONFIG_IOMMUFD_TEST.

/sys/bus/iommufd_mock covers both, it exists only once the module is
loaded and the kernel was built with CONFIG_IOMMUFD_TEST. Check for it
once before handing over to the harness, rather than in each of the
fixtures, and report a skip. test_harness_run() is what TEST_HARNESS_MAIN
calls anyway, so the tests still run exactly as they did.

Signed-off-by: Eva Kurchatova <eva.kurchatova@virtuozzo.com>
---
 tools/testing/selftests/iommu/iommufd.c          | 15 ++++++++++++++-
 tools/testing/selftests/iommu/iommufd_fail_nth.c | 15 ++++++++++++++-
 2 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/iommu/iommufd.c b/tools/testing/selftests/iommu/iommufd.c
index d44b34b05757..446306badcdc 100644
--- a/tools/testing/selftests/iommu/iommufd.c
+++ b/tools/testing/selftests/iommu/iommufd.c
@@ -3613,4 +3613,17 @@ TEST_F(iommufd_device_pasid, pasid_attach)
 	test_cmd_mock_domain_replace(self->stdev_id, self->ioas_id);
 }
 
-TEST_HARNESS_MAIN
+static bool iommufd_mock_available(void)
+{
+	return access("/sys/bus/iommufd_mock", F_OK) == 0;
+}
+
+int main(int argc, char **argv)
+{
+	if (!iommufd_mock_available())
+		ksft_exit_skip("no iommufd mock device, the tests need "
+			       "CONFIG_IOMMUFD_TEST=y and the iommufd "
+			       "module loaded\n");
+
+	return test_harness_run(argc, argv);
+}
diff --git a/tools/testing/selftests/iommu/iommufd_fail_nth.c b/tools/testing/selftests/iommu/iommufd_fail_nth.c
index 25495d8dceb3..c516e00f7316 100644
--- a/tools/testing/selftests/iommu/iommufd_fail_nth.c
+++ b/tools/testing/selftests/iommu/iommufd_fail_nth.c
@@ -745,4 +745,17 @@ TEST_FAIL_NTH(basic_fail_nth, device)
 	return 0;
 }
 
-TEST_HARNESS_MAIN
+static bool iommufd_mock_available(void)
+{
+	return access("/sys/bus/iommufd_mock", F_OK) == 0;
+}
+
+int main(int argc, char **argv)
+{
+	if (!iommufd_mock_available())
+		ksft_exit_skip("no iommufd mock device, the tests need "
+			       "CONFIG_IOMMUFD_TEST=y and the iommufd "
+			       "module loaded\n");
+
+	return test_harness_run(argc, argv);
+}
-- 
2.55.0