[PATCH v2 12/12] selftests: cgroup: Add functional tests for dynamic housekeeping

[Qiliang Yuan <realwujing@gmail.com>]

This extends the cgroup v2 testing framework in selftests to validate the
newly added Dynamic Housekeeping Management (DHM) cpuset interface:
`cpuset.housekeeping.cpus` and `cpuset.housekeeping.smt_aware`.

The `test_cpuset_housekeeping` functional test verifies:
- Validation of DHM's SMT safety guard (`cpuset.housekeeping.smt_aware`)
  by ensuring writing to it behaves as expected.
- Basic read and write capabilities of `cpuset.housekeeping.cpus` using
  the base CPU mask.

If the DHM functionality is not present in the kernel, the selftest skips gracefully.

Signed-off-by: Qiliang Yuan <realwujing@gmail.com>
---
 tools/testing/selftests/cgroup/test_cpuset.c | 36 ++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/tools/testing/selftests/cgroup/test_cpuset.c b/tools/testing/selftests/cgroup/test_cpuset.c
index c5cf8b56ceb8f..b2a032be4407a 100644
--- a/tools/testing/selftests/cgroup/test_cpuset.c
+++ b/tools/testing/selftests/cgroup/test_cpuset.c
@@ -232,6 +232,41 @@ static int test_cpuset_perms_subtree(const char *root)
 	return ret;
 }
 
+static int test_cpuset_housekeeping(const char *root)
+{
+	char buf[PAGE_SIZE];
+	int ret = KSFT_FAIL;
+
+	/* If the kernel doesn't have DHM patch, skip */
+	if (cg_read(root, "cpuset.housekeeping.cpus", buf, sizeof(buf)))
+		return KSFT_SKIP;
+
+	/* Test writing 1 and 0 to smt_aware */
+	if (cg_write(root, "cpuset.housekeeping.smt_aware", "1"))
+		goto cleanup;
+
+	if (cg_read_strstr(root, "cpuset.housekeeping.smt_aware", "1"))
+		goto cleanup;
+
+	if (cg_write(root, "cpuset.housekeeping.smt_aware", "0"))
+		goto cleanup;
+
+	if (cg_read_strstr(root, "cpuset.housekeeping.smt_aware", "0"))
+		goto cleanup;
+
+	/* Read root cpuset.cpus.effective */
+	if (cg_read(root, "cpuset.cpus.effective", buf, sizeof(buf)))
+		goto cleanup;
+	
+	/* Write it back to housekeeping.cpus */
+	if (cg_write(root, "cpuset.housekeeping.cpus", buf))
+		goto cleanup;
+
+	ret = KSFT_PASS;
+
+cleanup:
+	return ret;
+}
 
 #define T(x) { x, #x }
 struct cpuset_test {
@@ -241,6 +276,7 @@ struct cpuset_test {
 	T(test_cpuset_perms_object_allow),
 	T(test_cpuset_perms_object_deny),
 	T(test_cpuset_perms_subtree),
+	T(test_cpuset_housekeeping),
 };
 #undef T
 

-- 
2.43.0