39fcfb911c
EBB (Event Based Branches) are currently only available on POWER8, so we should skip them on other CPUs. I've found that at least one test loops forever on 970MP (cycles_with_freeze_test). Signed-off-by: Denis Kirjanov <kda@linux-powerpc.org> [mpe: Minor change log editing, add skip to cpu_event_vs_ebb_test] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
103 lines
2.3 KiB
C
103 lines
2.3 KiB
C
/*
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* Copyright 2014, Michael Ellerman, IBM Corp.
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* Licensed under GPLv2.
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*/
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#include <sched.h>
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#include <signal.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <sys/mman.h>
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#include "ebb.h"
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/*
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* Test that tries to trigger CPU_FTR_PMAO_BUG. Which is a hardware defect
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* where an exception triggers but we context switch before it is delivered and
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* lose the exception.
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*/
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static int test_body(void)
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{
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int i, orig_period, max_period;
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struct event event;
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SKIP_IF(!ebb_is_supported());
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/* We use PMC4 to make sure the kernel switches all counters correctly */
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event_init_named(&event, 0x40002, "instructions");
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event_leader_ebb_init(&event);
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event.attr.exclude_kernel = 1;
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event.attr.exclude_hv = 1;
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event.attr.exclude_idle = 1;
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FAIL_IF(event_open(&event));
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ebb_enable_pmc_counting(4);
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setup_ebb_handler(standard_ebb_callee);
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ebb_global_enable();
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FAIL_IF(ebb_event_enable(&event));
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/*
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* We want a low sample period, but we also want to get out of the EBB
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* handler without tripping up again.
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*
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* This value picked after much experimentation.
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*/
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orig_period = max_period = sample_period = 400;
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mtspr(SPRN_PMC4, pmc_sample_period(sample_period));
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while (ebb_state.stats.ebb_count < 1000000) {
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/*
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* We are trying to get the EBB exception to race exactly with
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* us entering the kernel to do the syscall. We then need the
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* kernel to decide our timeslice is up and context switch to
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* the other thread. When we come back our EBB will have been
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* lost and we'll spin in this while loop forever.
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*/
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for (i = 0; i < 100000; i++)
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sched_yield();
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/* Change the sample period slightly to try and hit the race */
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if (sample_period >= (orig_period + 200))
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sample_period = orig_period;
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else
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sample_period++;
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if (sample_period > max_period)
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max_period = sample_period;
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}
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ebb_freeze_pmcs();
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ebb_global_disable();
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count_pmc(4, sample_period);
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mtspr(SPRN_PMC4, 0xdead);
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dump_summary_ebb_state();
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dump_ebb_hw_state();
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event_close(&event);
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FAIL_IF(ebb_state.stats.ebb_count == 0);
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/* We vary our sample period so we need extra fudge here */
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FAIL_IF(!ebb_check_count(4, orig_period, 2 * (max_period - orig_period)));
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return 0;
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}
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static int lost_exception(void)
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{
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return eat_cpu(test_body);
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}
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int main(void)
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{
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return test_harness(lost_exception, "lost_exception");
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}
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