[LTP] [PATCH v5] high_freq_hwp_cap_cppc.c: new test

Piotr Kubaj
2026-03-23T10:56:35Z

Verify for all online logical CPUs that their highest performance value are
the same for HWP Capability MSR 0x771 and CPPC sysfs file.

Signed-off-by: Piotr Kubaj <piotr.kubaj@intel.com>
---
Address feedback with some changes:
- access() returns -1 on error,
- it also sets errno, so use that.

online check is excluded for cpu0 since it's always online.

runtest/power_management_tests | 1 +
testcases/kernel/power_management/.gitignore | 1 +
.../power_management/high_freq_hwp_cap_cppc.c | 84 +++++++++++++++++++
3 files changed, 86 insertions(+)
create mode 100644 testcases/kernel/power_management/high_freq_hwp_cap_cppc.c

diff --git a/runtest/power_management_tests b/runtest/power_management_tests
index 884e615cd..6d87dfb7f 100644
--- a/runtest/power_management_tests
+++ b/runtest/power_management_tests
@@ -1,4 +1,5 @@
#POWER_MANAGEMENT
+high_freq_hwp_cap_cppc high_freq_hwp_cap_cppc
runpwtests01 runpwtests01.sh
runpwtests02 runpwtests02.sh
runpwtests03 runpwtests03.sh
diff --git a/testcases/kernel/power_management/.gitignore b/testcases/kernel/power_management/.gitignore
index 0c2a3ed4b..c13bca1c4 100644
--- a/testcases/kernel/power_management/.gitignore
+++ b/testcases/kernel/power_management/.gitignore
@@ -1 +1,2 @@
+high_freq_hwp_cap_cppc
pm_get_sched_values
diff --git a/testcases/kernel/power_management/high_freq_hwp_cap_cppc.c b/testcases/kernel/power_management/high_freq_hwp_cap_cppc.c
new file mode 100644
index 000000000..648547f1c
--- /dev/null
+++ b/testcases/kernel/power_management/high_freq_hwp_cap_cppc.c
@@ -0,0 +1,84 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2026 Intel - http://www.intel.com/
+ */
+
+/*\
+ * Verify for all online logical CPUs that their highest performance value are
+ * the same for HWP Capability MSR 0x771 and CPPC sysfs file.
+ */
+
+#include "tst_test.h"
+#include "tst_safe_prw.h"
+
+static int nproc;
+
+static void setup(void)
+{
+ nproc = tst_ncpus();
+}
+
+static void run(void)
+{
+ bool status = true;
+
+ for (int i = 0; i < nproc; i++) {
+ bool online = false;
+ char path[PATH_MAX];
+ unsigned long long msr_highest_perf = 0, sysfs_highest_perf = 0;
+
+ snprintf(path, sizeof(path), "/sys/devices/system/cpu/cpu%d/online", i);
+ if (i)
+ SAFE_FILE_SCANF(path, "%d", &online);
+
+ if (!online) {
+ tst_res(TINFO, "CPU%d offline, skipping", i);
+ continue;
+ }
+
+ snprintf(path, sizeof(path), "/sys/devices/system/cpu/cpu%d/acpi_cppc/highest_perf", i);
+ if (access(path, F_OK) == -1) {
+ tst_res(TCONF | TERRNO, "CPPC sysfs not available, skipping");
+ return;
+ }
+
+ SAFE_FILE_SCANF(path, "%llu", &sysfs_highest_perf);
+ tst_res(TDEBUG, "%s: %llu", path, sysfs_highest_perf);
+
+ snprintf(path, sizeof(path), "/dev/cpu/%d/msr", i);
+ int fd = SAFE_OPEN(path, O_RDONLY);
+
+ SAFE_PREAD(1, fd, &msr_highest_perf, sizeof(msr_highest_perf), 0x771);
+ msr_highest_perf &= (1ULL << 8) - 1;
+ tst_res(TDEBUG, "%s: %llu", path, msr_highest_perf);
+
+ if (msr_highest_perf != sysfs_highest_perf) {
+ tst_res(TINFO, "cpu%d: sysfs=%llu MSR=%llu",
+ i, sysfs_highest_perf, msr_highest_perf);
+ status = false;
+ }
+
+ SAFE_CLOSE(fd);
+ }
+
+ if (status)
+ tst_res(TPASS, "Sysfs and MSR values are equal");
+ else
+ tst_res(TFAIL, "Highest performance values differ between sysfs and MSR");
+}
+
+static struct tst_test test = {
+ .needs_kconfigs = (const char *const []) {
+ "CONFIG_ACPI_CPPC_LIB",
+ "CONFIG_X86_MSR",
+ NULL
+ },
+ .needs_root = 1,
+ .setup = setup,
+ .supported_archs = (const char *const []) {
+ "x86",
+ "x86_64",
+ NULL
+ },
+ .test_all = run
+};
--
2.47.3

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