iommufd/selftest: Add a helper to get test device

commit 068e140
Author: Yi Liu <yi.l.liu@intel.com>
Date: Fri Mar 21 10:19:38 2025 -0700

    iommufd/selftest: Add a helper to get test device

    There is need to get the selftest device (sobj->type == TYPE_IDEV) in
    multiple places, so have a helper to for it.

    Link: https://patch.msgid.link/r/20250321171940.7213-17-yi.l.liu@intel.com
    Reviewed-by: Nicolin Chen <nicolinc@nvidia.com>
    Signed-off-by: Yi Liu <yi.l.liu@intel.com>
    Tested-by: Nicolin Chen <nicolinc@nvidia.com>
    Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

(cherry picked from commit 068e140)
Signed-off-by: Jerry Snitselaar <jsnitsel@redhat.com>
Upstream-Status: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
JIRA: https://issues.redhat.com/browse/RHEL-73600

Author: snits

drivers/iommu/iommufd/selftest.c

@@ -996,39 +996,49 @@ static int iommufd_test_mock_domain(struct iommufd_ucmd *ucmd,
 	return rc;
 }
 
-/* Replace the mock domain with a manually allocated hw_pagetable */
-static int iommufd_test_mock_domain_replace(struct iommufd_ucmd *ucmd,
-					    unsigned int device_id, u32 pt_id,
-					    struct iommu_test_cmd *cmd)
+static struct selftest_obj *
+iommufd_test_get_selftest_obj(struct iommufd_ctx *ictx, u32 id)
 {
 	struct iommufd_object *dev_obj;
 	struct selftest_obj *sobj;
-	int rc;
 
 	/*
 	 * Prefer to use the OBJ_SELFTEST because the destroy_rwsem will ensure
 	 * it doesn't race with detach, which is not allowed.
 	 */
-	dev_obj =
-		iommufd_get_object(ucmd->ictx, device_id, IOMMUFD_OBJ_SELFTEST);
+	dev_obj = iommufd_get_object(ictx, id, IOMMUFD_OBJ_SELFTEST);
 	if (IS_ERR(dev_obj))
-		return PTR_ERR(dev_obj);
+		return ERR_CAST(dev_obj);
 
 	sobj = to_selftest_obj(dev_obj);
 	if (sobj->type != TYPE_IDEV) {
-		rc = -EINVAL;
-		goto out_dev_obj;
+		iommufd_put_object(ictx, dev_obj);
+		return ERR_PTR(-EINVAL);
 	}
+	return sobj;
+}
+
+/* Replace the mock domain with a manually allocated hw_pagetable */
+static int iommufd_test_mock_domain_replace(struct iommufd_ucmd *ucmd,
+					    unsigned int device_id, u32 pt_id,
+					    struct iommu_test_cmd *cmd)
+{
+	struct selftest_obj *sobj;
+	int rc;
+
+	sobj = iommufd_test_get_selftest_obj(ucmd->ictx, device_id);
+	if (IS_ERR(sobj))
+		return PTR_ERR(sobj);
 
 	rc = iommufd_device_replace(sobj->idev.idev, IOMMU_NO_PASID, &pt_id);
 	if (rc)
-		goto out_dev_obj;
+		goto out_sobj;
 
 	cmd->mock_domain_replace.pt_id = pt_id;
 	rc = iommufd_ucmd_respond(ucmd, sizeof(*cmd));
 
-out_dev_obj:
-	iommufd_put_object(ucmd->ictx, dev_obj);
+out_sobj:
+	iommufd_put_object(ucmd->ictx, &sobj->obj);
 	return rc;
 }