selftests/powerpc/pmu/: Add interface test for mmcr2_fcs_fch fields

The testcases uses cycles event to verify the freeze counter settings in
Monitor Mode Control Register 2 (MMCR2). Event modifier (exclude_kernel)
setting is used for the event attribute to check the FCxS and FCxH (
Freeze counter in privileged and hypervisor state ) settings via perf
interface.

Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
[mpe: Add error checking, check MSR for MSR_HV, drop GET_MMCR_FIELD, add to .gitignore]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220127072012.662451-19-kjain@linux.ibm.com

tools/testing/selftests/powerpc/pmu/sampling_tests/.gitignore

@@ -6,3 +6,4 @@ mmcr0_fc56_pmc1ce_test
 mmcr0_fc56_pmc56_test
 mmcr1_comb_test
 mmcr2_l2l3_test
+mmcr2_fcs_fch_test

tools/testing/selftests/powerpc/pmu/sampling_tests/Makefile

@@ -3,7 +3,7 @@ CFLAGS += -m64
 
 TEST_GEN_PROGS := mmcr0_exceptionbits_test mmcr0_cc56run_test mmcr0_pmccext_test \
 		   mmcr0_pmcjce_test mmcr0_fc56_pmc1ce_test mmcr0_fc56_pmc56_test \
-		   mmcr1_comb_test mmcr2_l2l3_test
+		   mmcr1_comb_test mmcr2_l2l3_test mmcr2_fcs_fch_test
 
 top_srcdir = ../../../../../..
 include ../../../lib.mk

tools/testing/selftests/powerpc/pmu/sampling_tests/mmcr2_fcs_fch_test.c

@@ -0,0 +1,85 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2022, Madhavan Srinivasan, IBM Corp.
+ */
+
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+
+#include "../event.h"
+#include "misc.h"
+#include "utils.h"
+
+extern void thirty_two_instruction_loop(int loops);
+
+static bool is_hv;
+
+static void sig_usr2_handler(int signum, siginfo_t *info, void *data)
+{
+	ucontext_t *uctx = data;
+
+	is_hv = !!(uctx->uc_mcontext.gp_regs[PT_MSR] & MSR_HV);
+}
+
+/*
+ * A perf sampling test for mmcr2
+ * fields : fcs, fch.
+ */
+static int mmcr2_fcs_fch(void)
+{
+	struct sigaction sigact = {
+		.sa_sigaction = sig_usr2_handler,
+		.sa_flags = SA_SIGINFO
+	};
+	struct event event;
+	u64 *intr_regs;
+
+	FAIL_IF(sigaction(SIGUSR2, &sigact, NULL));
+	FAIL_IF(kill(getpid(), SIGUSR2));
+
+	/* Check for platform support for the test */
+	SKIP_IF(check_pvr_for_sampling_tests());
+
+	/* Init the event for the sampling test */
+	event_init_sampling(&event, 0x1001e);
+	event.attr.sample_regs_intr = platform_extended_mask;
+	event.attr.exclude_kernel = 1;
+	FAIL_IF(event_open(&event));
+	event.mmap_buffer = event_sample_buf_mmap(event.fd, 1);
+
+	FAIL_IF(event_enable(&event));
+
+	/* workload to make the event overflow */
+	thirty_two_instruction_loop(10000);
+
+	FAIL_IF(event_disable(&event));
+
+	/* Check for sample count */
+	FAIL_IF(!collect_samples(event.mmap_buffer));
+
+	intr_regs = get_intr_regs(&event, event.mmap_buffer);
+
+	/* Check for intr_regs */
+	FAIL_IF(!intr_regs);
+
+	/*
+	 * Verify that fcs and fch field of MMCR2 match
+	 * with corresponding modifier fields.
+	 */
+	if (is_hv)
+		FAIL_IF(event.attr.exclude_kernel !=
+			get_mmcr2_fch(get_reg_value(intr_regs, "MMCR2"), 1));
+	else
+		FAIL_IF(event.attr.exclude_kernel !=
+			get_mmcr2_fcs(get_reg_value(intr_regs, "MMCR2"), 1));
+
+	event_close(&event);
+	return 0;
+}
+
+int main(void)
+{
+	return test_harness(mmcr2_fcs_fch, "mmcr2_fcs_fch");
+}