3337bf41e0
An extra count on ebb_state.stats.pmc_count[PMC_INDEX(pmc)] is being per- formed when count_pmc() is used to reset PMCs on a few selftests. This extra pmc_count can occasionally invalidate results, such as the ones from cycles_test shown hereafter. The ebb_check_count() failed with an above the upper limit error due to the extra value on ebb_state.stats.pmc_count. Furthermore, this extra count is also indicated by extra PMC1 trace_log on the output of the cycle test (as well as on pmc56_overflow_test): ========== ... [21]: counter = 8 [22]: register SPRN_MMCR0 = 0x0000000080000080 [23]: register SPRN_PMC1 = 0x0000000080000004 [24]: counter = 9 [25]: register SPRN_MMCR0 = 0x0000000080000080 [26]: register SPRN_PMC1 = 0x0000000080000004 [27]: counter = 10 [28]: register SPRN_MMCR0 = 0x0000000080000080 [29]: register SPRN_PMC1 = 0x0000000080000004 >> [30]: register SPRN_PMC1 = 0x000000004000051e PMC1 count (0x280000546) above upper limit 0x2800003e8 (+0x15e) [FAIL] Test FAILED on line 52 failure: cycles ========== Signed-off-by: Desnes A. Nunes do Rosario <desnesn@linux.ibm.com> Tested-by: Sachin Sant <sachinp@linux.vnet.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20200626164737.21943-1-desnesn@linux.ibm.com
107 lines
2.0 KiB
C
107 lines
2.0 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright 2014, Michael Ellerman, IBM Corp.
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*/
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#include <sched.h>
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#include <signal.h>
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#include <stdbool.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include "ebb.h"
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/*
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* Test that the kernel properly handles PMAE across context switches.
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*
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* We test this by calling into the kernel inside our EBB handler, where PMAE
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* is clear. A cpu eater companion thread is running on the same CPU as us to
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* encourage the scheduler to switch us.
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*
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* The kernel must make sure that when it context switches us back in, it
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* honours the fact that we had PMAE clear.
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*
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* Observed to hit the failing case on the first EBB with a broken kernel.
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*/
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static bool mmcr0_mismatch;
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static uint64_t before, after;
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static void syscall_ebb_callee(void)
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{
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uint64_t val;
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val = mfspr(SPRN_BESCR);
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if (!(val & BESCR_PMEO)) {
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ebb_state.stats.spurious++;
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goto out;
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}
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ebb_state.stats.ebb_count++;
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count_pmc(1, sample_period);
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before = mfspr(SPRN_MMCR0);
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/* Try and get ourselves scheduled, to force a PMU context switch */
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sched_yield();
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after = mfspr(SPRN_MMCR0);
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if (before != after)
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mmcr0_mismatch = true;
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out:
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reset_ebb();
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}
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static int test_body(void)
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{
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struct event event;
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SKIP_IF(!ebb_is_supported());
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event_init_named(&event, 0x1001e, "cycles");
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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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setup_ebb_handler(syscall_ebb_callee);
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ebb_global_enable();
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FAIL_IF(ebb_event_enable(&event));
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mtspr(SPRN_PMC1, pmc_sample_period(sample_period));
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while (ebb_state.stats.ebb_count < 20 && !mmcr0_mismatch)
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FAIL_IF(core_busy_loop());
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ebb_global_disable();
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ebb_freeze_pmcs();
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dump_ebb_state();
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if (mmcr0_mismatch)
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printf("Saw MMCR0 before 0x%lx after 0x%lx\n", before, after);
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event_close(&event);
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FAIL_IF(ebb_state.stats.ebb_count == 0);
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FAIL_IF(mmcr0_mismatch);
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return 0;
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}
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int pmae_handling(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(pmae_handling, "pmae_handling");
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}
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