iommufd: Add a selftest

Cover the essential functionality of the iommufd with a directed test from
userspace. This aims to achieve reasonable functional coverage using the
in-kernel self test framework.

A second test does a failure injection sweep of the success paths to study
error unwind behaviors.

This allows achieving high coverage of the corner cases in pages.c.

The selftest requires CONFIG_IOMMUFD_TEST to be enabled, and several huge
pages which may require:

  echo 4 > /proc/sys/vm/nr_hugepages

Link: https://lore.kernel.org/r/[email protected]
Tested-by: Nicolin Chen <[email protected]>
Tested-by: Matthew Rosato <[email protected]> # s390
Tested-by: Yi Liu <[email protected]>
Tested-by: Eric Auger <[email protected]> # aarch64
Signed-off-by: Nicolin Chen <[email protected]>
Signed-off-by: Yi Liu <[email protected]>
Signed-off-by: Jason Gunthorpe <[email protected]>

Author: jgunthorpe

tools/testing/selftests/Makefile

@@ -27,6 +27,7 @@ TARGETS += ftrace
 TARGETS += futex
 TARGETS += gpio
 TARGETS += intel_pstate
+TARGETS += iommu
 TARGETS += ipc
 TARGETS += ir
 TARGETS += kcmp

tools/testing/selftests/iommu/.gitignore

@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0-only
+/iommufd
+/iommufd_fail_nth

tools/testing/selftests/iommu/Makefile

@@ -0,0 +1,12 @@
+# SPDX-License-Identifier: GPL-2.0-only
+CFLAGS += -Wall -O2 -Wno-unused-function
+CFLAGS += -I../../../../include/uapi/
+CFLAGS += -I../../../../include/
+
+CFLAGS += -D_GNU_SOURCE
+
+TEST_GEN_PROGS :=
+TEST_GEN_PROGS += iommufd
+TEST_GEN_PROGS += iommufd_fail_nth
+
+include ../lib.mk

tools/testing/selftests/iommu/config

@@ -0,0 +1,2 @@
+CONFIG_IOMMUFD
+CONFIG_IOMMUFD_TEST