Re: [LTP] high_freq_hwp_cap_cppc.c: new test

Re: [LTP] high_freq_hwp_cap_cppc.c: new test

[linuxtestproject.agent]

Hi Piotr,

On Mon, 20 Apr 2026, Piotr Kubaj wrote:
> high_freq_hwp_cap_cppc.c: new test

Reviewed-by: LTP AI Reviewer <ltp-ai@noreply.github.com>

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Re: [LTP] high_freq_hwp_cap_cppc.c: new test

[linuxtestproject.agent]

Hi Piotr,

On Mon, 4 May 2026 12:17:36 +0200, Piotr Kubaj wrote:
> high_freq_hwp_cap_cppc.c: new test
>
> Verify for all online logical CPUs that their highest performance value are
> the same for HWP Capability MSR 0x771 and CPPC sysfs file.

The body describes what the test does but not why it is needed. Please
add at least one sentence explaining the motivation — e.g. a known
inconsistency, a kernel regression, or a new interface being validated.

[...]

> +		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), MSR_HWP_CAPABILITIES);
> +		SAFE_CLOSE(fd);

If SAFE_PREAD aborts via tst_brk(), cleanup() is called but fd is never
closed because it is a loop-local variable with no cleanup handler.
Promote fd to a static (initialized to -1) and add a cleanup() that
guards with `if (fd != -1) SAFE_CLOSE(fd);`.

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Re: [LTP] high_freq_hwp_cap_cppc.c: new test

[linuxtestproject.agent]

Hi Piotr,

On Tue, 5 May 2026, Piotr Kubaj wrote:
> high_freq_hwp_cap_cppc.c: new test

Reviewed-by: LTP AI Reviewer <ltp-ai@noreply.github.com>

---
Note:

Our agent completed the review of the patch.

The agent can sometimes produce false positives although often its
findings are genuine. If you find issues with the review, please
comment this email or ignore the suggestions.

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Re: [LTP] high_freq_hwp_cap_cppc.c: new test

[linuxtestproject.agent]

Hi Piotr,

On Wed, 6 May 2026 14:56:51 +0200, Piotr Kubaj wrote:
> [PATCH] high_freq_hwp_cap_cppc.c: new test

> +static int *mismatch;
[...]
> +		if (msr_highest_perf != sysfs_highest_perf) {
> +			tst_res(TINFO, "cpu%d: sysfs=%llu MSR=%llu",
> +				i, sysfs_highest_perf, msr_highest_perf);
> +			mismatch[i] = 1;

`mismatch[]` is zeroed by SAFE_CALLOC in setup() but never cleared at the
start of run(). With -i N, stale flags from a prior iteration persist and
the per-CPU summary falsely reports "MISMATCH" for CPUs that are now
matching. Add:

    memset(mismatch, 0, nproc * sizeof(*mismatch));

at the top of run().

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Re: [LTP] high_freq_hwp_cap_cppc.c: new test

[linuxtestproject.agent]

Hi Piotr,

On 2026-05-07, Piotr Kubaj wrote:
> high_freq_hwp_cap_cppc.c: new test

> +	mismatch = SAFE_MALLOC(nproc, sizeof(int));

SAFE_MALLOC takes a single size argument. This will not compile.
Use SAFE_CALLOC(nproc, sizeof(int)) instead.

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[LTP] [PATCH v13] 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.

On HWP-capable x86 platforms the acpi_cppc/highest_perf sysfs attribute is
expected to reflect the same highest-performance value that firmware
programs into the HWP Capabilities MSR (0x771, bits 7:0). A mismatch
between the two interfaces indicates a kernel regression in how CPPC
values are exposed to userspace, and would break tools (e.g. cpupower,
intel_pstate tuning scripts) that rely on the sysfs interface to make
frequency-scaling decisions.

Signed-off-by: Piotr Kubaj <piotr.kubaj@intel.com>
---
Fix compilation error.
 runtest/power_management_tests                |   1 +
 testcases/kernel/power_management/.gitignore  |   1 +
 .../power_management/high_freq_hwp_cap_cppc.c | 114 ++++++++++++++++++
 3 files changed, 116 insertions(+)
 create mode 100644 testcases/kernel/power_management/.gitignore
 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 b670da6ec..4da57ee72 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
 runpwtests03 runpwtests03.sh
 runpwtests04 runpwtests04.sh
 runpwtests06 runpwtests06.sh
diff --git a/testcases/kernel/power_management/.gitignore b/testcases/kernel/power_management/.gitignore
new file mode 100644
index 000000000..03f0c83e4
--- /dev/null
+++ b/testcases/kernel/power_management/.gitignore
@@ -0,0 +1 @@
+high_freq_hwp_cap_cppc
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..a4f4d4197
--- /dev/null
+++ b/testcases/kernel/power_management/high_freq_hwp_cap_cppc.c
@@ -0,0 +1,114 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2026 Piotr Kubaj <piotr.kubaj@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.
+ *
+ * On HWP-capable x86 platforms the acpi_cppc/highest_perf sysfs attribute is
+ * expected to reflect the same highest-performance value that firmware
+ * programs into the HWP Capabilities MSR (0x771, bits 7:0). A mismatch
+ * between the two interfaces indicates a kernel regression in how CPPC
+ * values are exposed to userspace, and would break tools (e.g. cpupower,
+ * intel_pstate tuning scripts) that rely on the sysfs interface to make
+ * frequency-scaling decisions.
+ */
+
+#include "tst_test.h"
+#include "tst_safe_prw.h"
+
+#define MSR_HWP_CAPABILITIES	0x771
+#define HIGHEST_PERF_MASK	0xFF
+
+static int nproc;
+static int fd = -1;
+static int *mismatch;
+
+static void setup(void)
+{
+	if (access("/dev/cpu/0/msr", F_OK) == -1)
+		tst_brk(TCONF | TERRNO, "msr driver not loaded");
+
+	if (access("/sys/devices/system/cpu/cpu0/acpi_cppc/highest_perf", F_OK) == -1)
+		tst_brk(TCONF | TERRNO, "CPPC sysfs not available");
+
+	nproc = tst_ncpus_conf();
+	mismatch = SAFE_MALLOC(nproc * sizeof(int));
+}
+
+static void cleanup(void)
+{
+	if (fd != -1)
+		SAFE_CLOSE(fd);
+
+	free(mismatch);
+}
+
+static void run(void)
+{
+	bool status = true;
+	char path[PATH_MAX];
+
+	memset(mismatch, 0, nproc * sizeof(*mismatch));
+
+	for (int i = 0; i < nproc; i++) {
+		int online = 1;
+		unsigned long long msr_highest_perf = 0, sysfs_highest_perf = 0;
+
+		if (i) {
+			snprintf(path, sizeof(path), "/sys/devices/system/cpu/cpu%d/online", 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);
+		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);
+		fd = SAFE_OPEN(path, O_RDONLY);
+
+		SAFE_PREAD(1, fd, &msr_highest_perf, sizeof(msr_highest_perf), MSR_HWP_CAPABILITIES);
+		SAFE_CLOSE(fd);
+		msr_highest_perf &= HIGHEST_PERF_MASK;
+		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);
+			mismatch[i] = 1;
+			status = false;
+		}
+	}
+
+	for (int i = 0; i < nproc; i++)
+		tst_res(TINFO, "cpu%d: %s", i, mismatch[i] ? "MISMATCH" : "OK");
+
+	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,
+	.cleanup = cleanup,
+	.supported_archs = (const char *const []) {
+		"x86",
+		"x86_64",
+		NULL
+	},
+	.test_all = run
+};
-- 
2.47.3

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Re: [LTP] high_freq_hwp_cap_cppc.c: new test

[linuxtestproject.agent]

Hi Piotr,

On Thu, 14 May 2026, Piotr Kubaj wrote:
> high_freq_hwp_cap_cppc.c: new test

Reviewed-by: LTP AI Reviewer <ltp-ai@noreply.github.com>

---
Note:

Our agent completed the review of the patch.

The agent can sometimes produce false positives although often its
findings are genuine. If you find issues with the review, please
comment this email or ignore the suggestions.

Regards,
LTP AI Reviewer

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Mailing list info: https://lists.linux.it/listinfo/ltp