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// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright 2014, Michael Ellerman, IBM Corp.
*/
#include <sched.h>
#include <signal.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include "ebb.h"
/*
* Test that the kernel properly handles PMAE across context switches.
*
* We test this by calling into the kernel inside our EBB handler, where PMAE
* is clear. A cpu eater companion thread is running on the same CPU as us to
* encourage the scheduler to switch us.
*
* The kernel must make sure that when it context switches us back in, it
* honours the fact that we had PMAE clear.
*
* Observed to hit the failing case on the first EBB with a broken kernel.
*/
static bool mmcr0_mismatch;
static uint64_t before, after;
static void syscall_ebb_callee(void)
{
uint64_t val;
val = mfspr(SPRN_BESCR);
if (!(val & BESCR_PMEO)) {
ebb_state.stats.spurious++;
goto out;
}
ebb_state.stats.ebb_count++;
count_pmc(1, sample_period);
before = mfspr(SPRN_MMCR0);
/* Try and get ourselves scheduled, to force a PMU context switch */
sched_yield();
after = mfspr(SPRN_MMCR0);
if (before != after)
mmcr0_mismatch = true;
out:
reset_ebb();
}
static int test_body(void)
{
struct event event;
SKIP_IF(!ebb_is_supported());
event_init_named(&event, 0x1001e, "cycles");
event_leader_ebb_init(&event);
event.attr.exclude_kernel = 1;
event.attr.exclude_hv = 1;
event.attr.exclude_idle = 1;
FAIL_IF(event_open(&event));
setup_ebb_handler(syscall_ebb_callee);
ebb_global_enable();
FAIL_IF(ebb_event_enable(&event));
mtspr(SPRN_PMC1, pmc_sample_period(sample_period));
while (ebb_state.stats.ebb_count < 20 && !mmcr0_mismatch)
FAIL_IF(core_busy_loop());
ebb_global_disable();
ebb_freeze_pmcs();
count_pmc(1, sample_period);
dump_ebb_state();
if (mmcr0_mismatch)
printf("Saw MMCR0 before 0x%lx after 0x%lx\n", before, after);
event_close(&event);
FAIL_IF(ebb_state.stats.ebb_count == 0);
FAIL_IF(mmcr0_mismatch);
return 0;
}
int pmae_handling(void)
{
return eat_cpu(test_body);
}
int main(void)
{
return test_harness(pmae_handling, "pmae_handling");
}
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