iommu/selftest: prevent use of uninitialized variable

JIRA: https://issues.redhat.com/browse/RHEL-116573

Upstream Status: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git

commit 1d235d8
Author: Alessandro Zanni <alessandro.zanni87@gmail.com>
Date:   Wed Sep 24 19:16:28 2025 +0200

    iommu/selftest: prevent use of uninitialized variable

    Fix to avoid the usage of the `res` variable uninitialized in the
    following macro expansions.

    It solves the following warning:
    In function ‘iommufd_viommu_vdevice_alloc’,
      inlined from ‘wrapper_iommufd_viommu_vdevice_alloc’ at iommufd.c:2889:1:
    ../kselftest_harness.h:760:12: warning: ‘ret’ may be used uninitialized [-Wmaybe-uninitialized]
      760 |   if (!(__exp _t __seen)) { \
          |      ^
    ../kselftest_harness.h:513:9: note: in expansion of macro ‘__EXPECT’
      513 |   __EXPECT(expected, #expected, seen, #seen, ==, 1)
          |   ^~~~~~~~
    iommufd_utils.h:1057:9: note: in expansion of macro ‘ASSERT_EQ’
     1057 |   ASSERT_EQ(0, _test_cmd_trigger_vevents(self->fd, dev_id, nvevents))
          |   ^~~~~~~~~
    iommufd.c:2924:17: note: in expansion of macro ‘test_cmd_trigger_vevents’
     2924 |   test_cmd_trigger_vevents(dev_id, 3);
          |   ^~~~~~~~~~~~~~~~~~~~~~~~

    The issue can be reproduced, building the tests, with the command: make -C
    tools/testing/selftests TARGETS=iommu

    Link: https://patch.msgid.link/r/20250924171629.50266-1-alessandro.zanni87@gmail.com
    Fixes: 97717a1 ("iommufd/selftest: Add IOMMU_VEVENTQ_ALLOC test coverage")
    Signed-off-by: Alessandro Zanni <alessandro.zanni87@gmail.com>
    Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

Signed-off-by: Eder Zulian <ezulian@redhat.com>

Author: efzrh

tools/testing/selftests/iommu/iommufd_utils.h

@@ -1042,15 +1042,13 @@ static int _test_cmd_trigger_vevents(int fd, __u32 dev_id, __u32 nvevents)
 			.dev_id = dev_id,
 		},
 	};
-	int ret;
 
 	while (nvevents--) {
-		ret = ioctl(fd, _IOMMU_TEST_CMD(IOMMU_TEST_OP_TRIGGER_VEVENT),
-			    &trigger_vevent_cmd);
-		if (ret < 0)
+		if (!ioctl(fd, _IOMMU_TEST_CMD(IOMMU_TEST_OP_TRIGGER_VEVENT),
+			    &trigger_vevent_cmd))
 			return -1;
 	}
-	return ret;
+	return 0;
 }
 
 #define test_cmd_trigger_vevents(dev_id, nvevents) \