Messages in this thread | | | Subject | Re: [PATCH 2/2] powerpc/perf: Fix mmcra corruption by bhrb_filter | From | Ravi Bangoria <> | Date | Sat, 11 May 2019 08:17:21 +0530 |
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On 5/11/19 8:12 AM, Ravi Bangoria wrote: > Consider a scenario where user creates two events: > > 1st event: > attr.sample_type |= PERF_SAMPLE_BRANCH_STACK; > attr.branch_sample_type = PERF_SAMPLE_BRANCH_ANY; > fd = perf_event_open(attr, 0, 1, -1, 0); > > This sets cpuhw->bhrb_filter to 0 and returns valid fd. > > 2nd event: > attr.sample_type |= PERF_SAMPLE_BRANCH_STACK; > attr.branch_sample_type = PERF_SAMPLE_BRANCH_CALL; > fd = perf_event_open(attr, 0, 1, -1, 0); > > It overrides cpuhw->bhrb_filter to -1 and returns with error. > > Now if power_pmu_enable() gets called by any path other than > power_pmu_add(), ppmu->config_bhrb(-1) will set mmcra to -1. > > Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Fixes: 3925f46bb590 ("powerpc/perf: Enable branch stack sampling framework")
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