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author | Michael Ellerman <mpe@ellerman.id.au> | 2014-06-10 22:23:10 +1000 |
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committer | Benjamin Herrenschmidt <benh@kernel.crashing.org> | 2014-06-11 17:03:58 +1000 |
commit | 3752e453f6bafd78e5586cc2b2e33ee4b6e1566d (patch) | |
tree | 2c5d88b6d9f759844249a36ce8b729dcb5c274ad /tools/testing/selftests/powerpc/pmu/ebb/pmae_handling_test.c | |
parent | 33b4819f3b93bbcb934e02cbc64ff3c5e9d0149b (diff) | |
download | linux-stable-3752e453f6bafd78e5586cc2b2e33ee4b6e1566d.tar.gz linux-stable-3752e453f6bafd78e5586cc2b2e33ee4b6e1566d.tar.bz2 linux-stable-3752e453f6bafd78e5586cc2b2e33ee4b6e1566d.zip |
selftests/powerpc: Add tests of PMU EBBs
The Power8 Performance Monitor Unit (PMU) has a new feature called Event
Based Branches (EBB). This commit adds tests of the kernel API for using
EBBs.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'tools/testing/selftests/powerpc/pmu/ebb/pmae_handling_test.c')
-rw-r--r-- | tools/testing/selftests/powerpc/pmu/ebb/pmae_handling_test.c | 106 |
1 files changed, 106 insertions, 0 deletions
diff --git a/tools/testing/selftests/powerpc/pmu/ebb/pmae_handling_test.c b/tools/testing/selftests/powerpc/pmu/ebb/pmae_handling_test.c new file mode 100644 index 000000000000..986500fd2131 --- /dev/null +++ b/tools/testing/selftests/powerpc/pmu/ebb/pmae_handling_test.c @@ -0,0 +1,106 @@ +/* + * Copyright 2014, Michael Ellerman, IBM Corp. + * Licensed under GPLv2. + */ + +#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; + + 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"); +} |