3.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
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 <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/powerpc/perf/core-book3s.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c
@@ -1307,6 +1307,9 @@ static void power_pmu_enable(struct 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
write_mmcr0(cpuhw, mmcr0);
- if (ppmu->flags & PPMU_ARCH_207S)
- mtspr(SPRN_MMCR2, 0);
-
/*
* Enable instruction sampling if necessary
*/
--
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