LXR linux/tools/testing/selftests/powerpc/pmu/ebb/pmae_handling

   1/*
   2 * Copyright 2014, Michael Ellerman, IBM Corp.
   3 * Licensed under GPLv2.
   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        count_pmc(1, sample_period);
  86
  87        dump_ebb_state();
  88
  89        if (mmcr0_mismatch)
  90                printf("Saw MMCR0 before 0x%lx after 0x%lx\n", before, after);
  91
  92        event_close(&event);
  93
  94        FAIL_IF(ebb_state.stats.ebb_count == 0);
  95        FAIL_IF(mmcr0_mismatch);
  96
  97        return 0;
  98}
  99
 100int pmae_handling(void)
 101{
 102        return eat_cpu(test_body);
 103}
 104
 105int main(void)
 106{
 107        return test_harness(pmae_handling, "pmae_handling");
 108}
 109