pmae_handling_test.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Copyright 2014, Michael Ellerman, IBM Corp.
  4 */
  5
  6#include <sched.h>
  7#include <signal.h>
  8#include <stdbool.h>
  9#include <stdio.h>
 10#include <stdlib.h>
 11
 12#include "ebb.h"
 13
 14
 15/*
 16 * Test that the kernel properly handles PMAE across context switches.
 17 *
 18 * We test this by calling into the kernel inside our EBB handler, where PMAE
 19 * is clear. A cpu eater companion thread is running on the same CPU as us to
 20 * encourage the scheduler to switch us.
 21 *
 22 * The kernel must make sure that when it context switches us back in, it
 23 * honours the fact that we had PMAE clear.
 24 *
 25 * Observed to hit the failing case on the first EBB with a broken kernel.
 26 */
 27
 28static bool mmcr0_mismatch;
 29static uint64_t before, after;
 30
 31static void syscall_ebb_callee(void)
 32{
 33	uint64_t val;
 34
 35	val = mfspr(SPRN_BESCR);
 36	if (!(val & BESCR_PMEO)) {
 37		ebb_state.stats.spurious++;
 38		goto out;
 39	}
 40
 41	ebb_state.stats.ebb_count++;
 42	count_pmc(1, sample_period);
 43
 44	before = mfspr(SPRN_MMCR0);
 45
 46	/* Try and get ourselves scheduled, to force a PMU context switch */
 47	sched_yield();
 48
 49	after = mfspr(SPRN_MMCR0);
 50	if (before != after)
 51		mmcr0_mismatch = true;
 52
 53out:
 54	reset_ebb();
 55}
 56
 57static int test_body(void)
 58{
 59	struct event event;
 60
 61	SKIP_IF(!ebb_is_supported());
 62
 63	event_init_named(&event, 0x1001e, "cycles");
 64	event_leader_ebb_init(&event);
 65
 66	event.attr.exclude_kernel = 1;
 67	event.attr.exclude_hv = 1;
 68	event.attr.exclude_idle = 1;
 69
 70	FAIL_IF(event_open(&event));
 71
 72	setup_ebb_handler(syscall_ebb_callee);
 73	ebb_global_enable();
 74
 75	FAIL_IF(ebb_event_enable(&event));
 76
 77	mtspr(SPRN_PMC1, pmc_sample_period(sample_period));
 78
 79	while (ebb_state.stats.ebb_count < 20 && !mmcr0_mismatch)
 80		FAIL_IF(core_busy_loop());
 81
 82	ebb_global_disable();
 83	ebb_freeze_pmcs();
 84
 85	dump_ebb_state();
 86
 87	if (mmcr0_mismatch)
 88		printf("Saw MMCR0 before 0x%lx after 0x%lx\n", before, after);
 89
 90	event_close(&event);
 91
 92	FAIL_IF(ebb_state.stats.ebb_count == 0);
 93	FAIL_IF(mmcr0_mismatch);
 94
 95	return 0;
 96}
 97
 98int pmae_handling(void)
 99{
100	return eat_cpu(test_body);
101}
102
103int main(void)
104{
105	return test_harness(pmae_handling, "pmae_handling");
106}