diff --git a/drivers/iommu/iommufd/fault.c b/drivers/iommu/iommufd/fault.c
index 053b0e30f55a..1fe804e28a86 100644
--- a/drivers/iommu/iommufd/fault.c
+++ b/drivers/iommu/iommufd/fault.c
@@ -420,8 +420,6 @@ out_put_fdno:
 	put_unused_fd(fdno);
 out_fput:
 	fput(filep);
-	refcount_dec(&fault->obj.users);
-	iommufd_ctx_put(fault->ictx);
 out_abort:
 	iommufd_object_abort_and_destroy(ucmd->ictx, &fault->obj);
 
diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h
index 059b6537f2b7..34810f6ae2b5 100644
--- a/include/uapi/linux/iommufd.h
+++ b/include/uapi/linux/iommufd.h
@@ -297,7 +297,7 @@ struct iommu_ioas_unmap {
  *                       ioctl(IOMMU_OPTION_HUGE_PAGES)
  * @IOMMU_OPTION_RLIMIT_MODE:
  *    Change how RLIMIT_MEMLOCK accounting works. The caller must have privilege
- *    to invoke this. Value 0 (default) is user based accouting, 1 uses process
+ *    to invoke this. Value 0 (default) is user based accounting, 1 uses process
  *    based accounting. Global option, object_id must be 0
  * @IOMMU_OPTION_HUGE_PAGES:
  *    Value 1 (default) allows contiguous pages to be combined when generating
@@ -390,7 +390,7 @@ struct iommu_vfio_ioas {
  * @IOMMU_HWPT_ALLOC_PASID: Requests a domain that can be used with PASID. The
  *                          domain can be attached to any PASID on the device.
  *                          Any domain attached to the non-PASID part of the
- *                          device must also be flaged, otherwise attaching a
+ *                          device must also be flagged, otherwise attaching a
  *                          PASID will blocked.
  *                          If IOMMU does not support PASID it will return
  *                          error (-EOPNOTSUPP).
@@ -558,16 +558,25 @@ struct iommu_hw_info_vtd {
  * For the details of @idr, @iidr and @aidr, please refer to the chapters
  * from 6.3.1 to 6.3.6 in the SMMUv3 Spec.
  *
- * User space should read the underlying ARM SMMUv3 hardware information for
- * the list of supported features.
+ * This reports the raw HW capability, and not all bits are meaningful to be
+ * read by userspace. Only the following fields should be used:
  *
- * Note that these values reflect the raw HW capability, without any insight if
- * any required kernel driver support is present. Bits may be set indicating the
- * HW has functionality that is lacking kernel software support, such as BTM. If
- * a VMM is using this information to construct emulated copies of these
- * registers it should only forward bits that it knows it can support.
+ * idr[0]: ST_LEVEL, TERM_MODEL, STALL_MODEL, TTENDIAN , CD2L, ASID16, TTF
+ * idr[1]: SIDSIZE, SSIDSIZE
+ * idr[3]: BBML, RIL
+ * idr[5]: VAX, GRAN64K, GRAN16K, GRAN4K
  *
- * In future, presence of required kernel support will be indicated in flags.
+ * - S1P should be assumed to be true if a NESTED HWPT can be created
+ * - VFIO/iommufd only support platforms with COHACC, it should be assumed to be
+ *   true.
+ * - ATS is a per-device property. If the VMM describes any devices as ATS
+ *   capable in ACPI/DT it should set the corresponding idr.
+ *
+ * This list may expand in future (eg E0PD, AIE, PBHA, D128, DS etc). It is
+ * important that VMMs do not read bits outside the list to allow for
+ * compatibility with future kernels. Several features in the SMMUv3
+ * architecture are not currently supported by the kernel for nesting: HTTU,
+ * BTM, MPAM and others.
  */
 struct iommu_hw_info_arm_smmuv3 {
 	__u32 flags;
@@ -766,7 +775,7 @@ struct iommu_hwpt_vtd_s1_invalidate {
 };
 
 /**
- * struct iommu_viommu_arm_smmuv3_invalidate - ARM SMMUv3 cahce invalidation
+ * struct iommu_viommu_arm_smmuv3_invalidate - ARM SMMUv3 cache invalidation
  *         (IOMMU_VIOMMU_INVALIDATE_DATA_ARM_SMMUV3)
  * @cmd: 128-bit cache invalidation command that runs in SMMU CMDQ.
  *       Must be little-endian.
diff --git a/tools/testing/selftests/iommu/iommufd_fail_nth.c b/tools/testing/selftests/iommu/iommufd_fail_nth.c
index 22f6fd5f0f74..64b1f8e1b0cf 100644
--- a/tools/testing/selftests/iommu/iommufd_fail_nth.c
+++ b/tools/testing/selftests/iommu/iommufd_fail_nth.c
@@ -615,7 +615,12 @@ TEST_FAIL_NTH(basic_fail_nth, access_pin_domain)
 /* device.c */
 TEST_FAIL_NTH(basic_fail_nth, device)
 {
+	struct iommu_hwpt_selftest data = {
+		.iotlb = IOMMU_TEST_IOTLB_DEFAULT,
+	};
 	struct iommu_test_hw_info info;
+	uint32_t fault_id, fault_fd;
+	uint32_t fault_hwpt_id;
 	uint32_t ioas_id;
 	uint32_t ioas_id2;
 	uint32_t stdev_id;
@@ -678,6 +683,15 @@ TEST_FAIL_NTH(basic_fail_nth, device)
 	if (_test_cmd_vdevice_alloc(self->fd, viommu_id, idev_id, 0, &vdev_id))
 		return -1;
 
+	if (_test_ioctl_fault_alloc(self->fd, &fault_id, &fault_fd))
+		return -1;
+	close(fault_fd);
+
+	if (_test_cmd_hwpt_alloc(self->fd, idev_id, hwpt_id, fault_id,
+				 IOMMU_HWPT_FAULT_ID_VALID, &fault_hwpt_id,
+				 IOMMU_HWPT_DATA_SELFTEST, &data, sizeof(data)))
+		return -1;
+
 	return 0;
 }