selftests/powerpc/pmu: Add interface test for bhrb disable field for non-branch samples

The testcase uses "instructions" event to generate the samples and fetch
Monitor Mode Control Register A (MMCRA) when overflow. Branch History
Rolling Buffer(bhrb) disable bit is part of MMCRA which need to be
verified by perf interface. Incase sample is not of branch type, bhrb
disable bit is explicitly set to 1. Testcase checks if the bhrb disable
bit is set of MMCRA register via perf interface for ISA v3.1 platform
Signed-off-by: Kajol Jain <kjain@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220610134113.62991-15-atrajeev@linux.vnet.ibm.com

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

@@ -7,7 +7,7 @@ TEST_GEN_PROGS := mmcr0_exceptionbits_test mmcr0_cc56run_test mmcr0_pmccext_test
 		   mmcr3_src_test mmcra_thresh_marked_sample_test mmcra_thresh_cmp_test \
 		   mmcra_bhrb_ind_call_test mmcra_bhrb_any_test mmcra_bhrb_cond_test \
 		   mmcra_bhrb_disable_test bhrb_no_crash_wo_pmu_test intr_regs_no_crash_wo_pmu_test \
-		   bhrb_filter_map_test mmcr1_sel_unit_cache_test
+		   bhrb_filter_map_test mmcr1_sel_unit_cache_test mmcra_bhrb_disable_no_branch_test
 
 top_srcdir = ../../../../../..
 include ../../../lib.mk

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

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2022, Kajol Jain, IBM Corp.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "../event.h"
+#include "misc.h"
+#include "utils.h"
+
+extern void thirty_two_instruction_loop(int loops);
+
+/* Instructions */
+#define EventCode 0x500fa
+
+/*
+ * A perf sampling test for mmcra
+ * field: bhrb_disable.
+ */
+static int mmcra_bhrb_disable_no_branch_test(void)
+{
+	struct event event;
+	u64 *intr_regs;
+
+	/*
+	 * Check for platform support for the test.
+	 * This test is only aplicable on power10
+	 */
+	SKIP_IF(check_pvr_for_sampling_tests());
+	SKIP_IF(!have_hwcap2(PPC_FEATURE2_ARCH_3_1));
+
+	 /* Init the event for the sampling test */
+	event_init_sampling(&event, EventCode);
+	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));
+
+	intr_regs = get_intr_regs(&event, event.mmap_buffer);
+
+	/* Check for intr_regs */
+	FAIL_IF(!intr_regs);
+
+	/* Verify that bhrb_disable bit is set in MMCRA for non-branch samples */
+	FAIL_IF(!get_mmcra_bhrb_disable(get_reg_value(intr_regs, "MMCRA"), 5));
+
+	event_close(&event);
+	return 0;
+}
+
+int main(void)
+{
+	return test_harness(mmcra_bhrb_disable_no_branch_test, "mmcra_bhrb_disable_no_branch_test");
+}