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powerpc/perf: Fix MMCR2 handling for EBB

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In the recent commit b50a6c584b "Clear MMCR2 when enabling PMU", I
screwed up the handling of MMCR2 for tasks using EBB.

We must make sure we set MMCR2 *before* ebb_switch_in(), otherwise we
overwrite the value of MMCR2 that userspace may have written. That
potentially breaks a task that uses EBB and manually uses MMCR2 for
event freezing.

Fixes: b50a6c584b ("powerpc/perf: Clear MMCR2 when enabling PMU")
Cc: stable@vger.kernel.org
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Michael Ellerman 2014-07-23 17:20:04 +10:00 committed by Benjamin Herrenschmidt
parent 6f5405bc2e
commit 8903461c9b
1 changed files with 3 additions and 3 deletions
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6
arch/powerpc/perf/core-book3s.c
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@ -1307,6 +1307,9 @@ static void power_pmu_enable(struct pmu *pmu)
out_enable:
pmao_restore_workaround(ebb);
if (ppmu->flags & PPMU_ARCH_207S)
mtspr(SPRN_MMCR2, 0);
mmcr0 = ebb_switch_in(ebb, cpuhw->mmcr[0]);
mb();
@ -1315,9 +1318,6 @@ static void power_pmu_enable(struct pmu *pmu)
write_mmcr0(cpuhw, mmcr0);
if (ppmu->flags & PPMU_ARCH_207S)
mtspr(SPRN_MMCR2, 0);
/*
* Enable instruction sampling if necessary
*/