Commit 8903461c authored Jul 23, 2014 by Michael Ellerman Committed by Benjamin Herrenschmidt Jul 23, 2014

powerpc/perf: Fix MMCR2 handling for EBB



In the recent commit b50a6c58 "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: b50a6c58 ("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>

parent 6f5405bc

arch/powerpc/perf/core-book3s.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -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
		*/