[LTP] [PATCH v4] high_freq_hwp_cap_cppc.c: new test

[LTP] [PATCH v4] high_freq_hwp_cap_cppc.c: new test

[Piotr Kubaj]

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>
---
Since SAFE_PREAD() already checks return code, remove the check.
 runtest/power_management_tests                |  1 +
 testcases/kernel/power_management/.gitignore  |  1 +
 .../power_management/high_freq_hwp_cap_cppc.c | 65 +++++++++++++++++++
 3 files changed, 67 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..99918906c
--- /dev/null
+++ b/testcases/kernel/power_management/high_freq_hwp_cap_cppc.c
@@ -0,0 +1,65 @@
+// 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++) {
+		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/acpi_cppc/highest_perf", i);
+		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)
+			status = false;
+	}
+
+	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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Re: [LTP] [PATCH v4] high_freq_hwp_cap_cppc.c: new test

[Andrea Cervesato via ltp]

Hi Piotr,

A few issues below.

> +// SPDX-License-Identifier: GPL-2.0-or-later
> +
> +/*
> + * Copyright (C) 2026 Intel - http://www.intel.com/

The blank line between the SPDX identifier and the copyright block is
non-standard. They should be adjacent (no blank line between them).

> +	nproc = tst_ncpus();

tst_ncpus() returns _SC_NPROCESSORS_ONLN — the *count* of online CPUs,
not the highest CPU number. On a system where CPUs 0, 1, 3 are online
and CPU 2 is offline, tst_ncpus() returns 3, and the loop below iterates
over CPUs 0, 1, 2, accessing the wrong set of sysfs paths.

Use tst_ncpus_conf() as the upper bound and skip offline CPUs
individually, or iterate over the actual online CPU numbers from
/sys/devices/system/cpu/online.

> +		snprintf(path, sizeof(path), "/sys/devices/system/cpu/cpu%d/acpi_cppc/highest_perf", i);
> +		SAFE_FILE_SCANF(path, "%llu", &sysfs_highest_perf);

CONFIG_ACPI_CPPC_LIB=y does not guarantee the acpi_cppc/ sysfs
directory exists at runtime — it only appears when the CPU firmware
exposes the CPPC _CPC ACPI method. If the path is absent, SAFE_FILE_SCANF
aborts with TBROK. Check for existence and return TCONF instead:

  if (access(path, F_OK)) {
      tst_res(TCONF, "CPPC sysfs not available, skipping");
      return;
  }

> +		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)
> +			status = false;

Two issues:

1. fd is never closed. Opening it once per CPU iteration leaks one
   file descriptor per CPU. Add SAFE_CLOSE(fd) at the end of the loop
   body.

2. When the values differ, status is set to false but there is no
   per-CPU message. The single TFAIL at the end gives no indication of
   which CPU triggered the failure. Add a TINFO or TFAIL per CPU:

     tst_res(TFAIL, "cpu%d: sysfs=%llu MSR=%llu",
             i, sysfs_highest_perf, msr_highest_perf);


Regards,
--
Andrea Cervesato
SUSE QE Automation Engineer Linux
andrea.cervesato@suse.com

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