2 * Copyright 2014, Michael Ellerman, IBM Corp.
3 * Licensed under GPLv2.
16 * Test that the kernel properly handles PMAE across context switches.
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.
22 * The kernel must make sure that when it context switches us back in, it
23 * honours the fact that we had PMAE clear.
25 * Observed to hit the failing case on the first EBB with a broken kernel.
28 static bool mmcr0_mismatch;
29 static uint64_t before, after;
31 static void syscall_ebb_callee(void)
35 val = mfspr(SPRN_BESCR);
36 if (!(val & BESCR_PMEO)) {
37 ebb_state.stats.spurious++;
41 ebb_state.stats.ebb_count++;
42 count_pmc(1, sample_period);
44 before = mfspr(SPRN_MMCR0);
46 /* Try and get ourselves scheduled, to force a PMU context switch */
49 after = mfspr(SPRN_MMCR0);
51 mmcr0_mismatch = true;
57 static int test_body(void)
61 event_init_named(&event, 0x1001e, "cycles");
62 event_leader_ebb_init(&event);
64 event.attr.exclude_kernel = 1;
65 event.attr.exclude_hv = 1;
66 event.attr.exclude_idle = 1;
68 FAIL_IF(event_open(&event));
70 setup_ebb_handler(syscall_ebb_callee);
73 FAIL_IF(ebb_event_enable(&event));
75 mtspr(SPRN_PMC1, pmc_sample_period(sample_period));
77 while (ebb_state.stats.ebb_count < 20 && !mmcr0_mismatch)
78 FAIL_IF(core_busy_loop());
83 count_pmc(1, sample_period);
88 printf("Saw MMCR0 before 0x%lx after 0x%lx\n", before, after);
92 FAIL_IF(ebb_state.stats.ebb_count == 0);
93 FAIL_IF(mmcr0_mismatch);
98 int pmae_handling(void)
100 return eat_cpu(test_body);
105 return test_harness(pmae_handling, "pmae_handling");