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Date:	Fri,  8 Aug 2014 13:40:07 -0700
From:	Kamal Mostafa <>
Cc:	Michael Ellerman <>,
	Benjamin Herrenschmidt <>,
	Kamal Mostafa <>
Subject: [PATCH 3.13 184/259] powerpc/perf: Fix MMCR2 handling for EBB -stable review patch.  If anyone has any objections, please let me know.


From: Michael Ellerman <>

commit 8903461c9bc56fcb041fb92d054e2529951770b6 upstream.

In the recent commit b50a6c584bb4 "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: b50a6c584bb4 ("powerpc/perf: Clear MMCR2 when enabling PMU")
Signed-off-by: Michael Ellerman <>
Signed-off-by: Benjamin Herrenschmidt <>
Signed-off-by: Kamal Mostafa <>
 arch/powerpc/perf/core-book3s.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
index 57a8ff9..36a8bdd 100644
--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c
@@ -1159,14 +1159,14 @@ static void power_pmu_enable(struct pmu *pmu)
 	cpuhw->mmcr[0] |= MMCR0_PMXE | MMCR0_FCECE;
+	if (ppmu->flags & PPMU_ARCH_207S)
+		mtspr(SPRN_MMCR2, 0);
 	mmcr0 = ebb_switch_in(ebb, cpuhw->mmcr[0]);
 	write_mmcr0(cpuhw, mmcr0);
-	if (ppmu->flags & PPMU_ARCH_207S)
-		mtspr(SPRN_MMCR2, 0);
 	 * Enable instruction sampling if necessary

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