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}
107