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 | |
28 | static bool mmcr0_mismatch; |
29 | static uint64_t before, after; |
30 | |
31 | static 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(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 | |
53 | out: |
54 | reset_ebb(); |
55 | } |
56 | |
57 | static int test_body(void) |
58 | { |
59 | struct event event; |
60 | |
61 | SKIP_IF(!ebb_is_supported()); |
62 | |
63 | event_init_named(e: &event, config: 0x1001e, name: "cycles" ); |
64 | event_leader_ebb_init(e: &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(e: &event)); |
71 | |
72 | setup_ebb_handler(syscall_ebb_callee); |
73 | ebb_global_enable(); |
74 | |
75 | FAIL_IF(ebb_event_enable(e: &event)); |
76 | |
77 | mtspr(SPRN_PMC1, pmc_sample_period(value: 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(e: &event); |
91 | |
92 | FAIL_IF(ebb_state.stats.ebb_count == 0); |
93 | FAIL_IF(mmcr0_mismatch); |
94 | |
95 | return 0; |
96 | } |
97 | |
98 | int pmae_handling(void) |
99 | { |
100 | return eat_cpu(test_function: test_body); |
101 | } |
102 | |
103 | int main(void) |
104 | { |
105 | return test_harness(pmae_handling, "pmae_handling" ); |
106 | } |
107 | |