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powerpc/perf: Fix MMCRA corruption by bhrb_filter

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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.

Fixes: 3925f46bb5 ("powerpc/perf: Enable branch stack sampling framework")
Cc: stable@vger.kernel.org # v3.10+
Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Reviewed-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Ravi Bangoria
2019-05-11 08:12:17 +05:30
committed by Michael Ellerman
parent b59bd3527f
commit 3202e35ec1
3 changed files with 10 additions and 2 deletions
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3
arch/powerpc/perf/power8-pmu.c
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@@ -29,6 +29,7 @@ enum {
#define POWER8_MMCRA_IFM1 0x0000000040000000UL
#define POWER8_MMCRA_IFM2 0x0000000080000000UL
#define POWER8_MMCRA_IFM3 0x00000000C0000000UL
#define POWER8_MMCRA_BHRB_MASK 0x00000000C0000000UL
/*
* Raw event encoding for PowerISA v2.07 (Power8):
@@ -243,6 +244,8 @@ static u64 power8_bhrb_filter_map(u64 branch_sample_type)
static void power8_config_bhrb(u64 pmu_bhrb_filter)
{
pmu_bhrb_filter &= POWER8_MMCRA_BHRB_MASK;
/* Enable BHRB filter in PMU */
mtspr(SPRN_MMCRA, (mfspr(SPRN_MMCRA) | pmu_bhrb_filter));
}