iommufd/selftest: Add coverage for vdevice tombstone

This tests the flow to tombstone vdevice when idevice is to be unbound
before vdevice destruction. The expected results of the tombstone are:

- The vdevice ID can't be reused anymore (not tested in this patch).
- Even ioctl(IOMMU_DESTROY) can't free the vdevice ID.
- iommufd_fops_release() can still free everything.

Link: https://patch.msgid.link/r/[e-mail]
Reviewed-by: Nicolin Chen <[e-mail]>
Tested-by: Nicolin Chen <[e-mail]>
Signed-off-by: Xu Yilun <[e-mail]>
Signed-off-by: Jason Gunthorpe <[e-mail]>

tools/testing/selftests/iommu/iommufd.c

···
 	test_ioctl_ioas_unmap(iova, PAGE_SIZE);
 }
 
+TEST_F(iommufd_viommu, vdevice_tombstone)
+{
+	uint32_t viommu_id = self->viommu_id;
+	uint32_t dev_id = self->device_id;
+	uint32_t vdev_id = 0;
+
+	if (!dev_id)
+		SKIP(return, "Skipping test for variant no_viommu");
+
+	test_cmd_vdevice_alloc(viommu_id, dev_id, 0x99, &vdev_id);
+	test_ioctl_destroy(self->stdev_id);
+	EXPECT_ERRNO(ENOENT, _test_ioctl_destroy(self->fd, vdev_id));
+}
+
 FIXTURE(iommufd_device_pasid)
 {
 	int fd;