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From: Julien Thierry <julien.thierry@arm.com>
To: linux-arm-kernel@lists.infradead.org
Cc: mark.rutland@arm.com, Julien Thierry <julien.thierry@arm.com>,
	peterz@infradead.org, jolsa@redhat.com, will.deacon@arm.com,
	Russell King <linux@armlinux.org.uk>,
	acme@kernel.org, alexander.shishkin@linux.intel.com,
	mingo@redhat.com, stable@vger.kernel.org, namhyung@kernel.org,
	sthotton@marvell.com, liwei391@huawei.com
Subject: [PATCH v4 3/9] arm: perf: save/resore pmsel
Date: Wed, 17 Jul 2019 09:17:06 +0100
Message-ID: <1563351432-55652-4-git-send-email-julien.thierry@arm.com> (raw)
In-Reply-To: <1563351432-55652-1-git-send-email-julien.thierry@arm.com>

The callback pmu->read() can be called with interrupts enabled.
Currently, on ARM, this can cause the following callchain:

armpmu_read() -> armpmu_event_update() -> armv7pmu_read_counter()

The last function might modify the counter selector register and then
read the target counter, without taking any lock. With interrupts
enabled, a PMU interrupt could occur and modify the selector register
as well, between the selection and read of the interrupted context.

Save and restore the value of the selector register in the PMU interrupt
handler, ensuring the interrupted context is left with the correct PMU
registers selected.

Signed-off-by: Julien Thierry <julien.thierry@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: stable@vger.kernel.org
---
 arch/arm/kernel/perf_event_v7.c | 25 +++++++++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/arch/arm/kernel/perf_event_v7.c b/arch/arm/kernel/perf_event_v7.c
index a4fb0f8..b7be2a3 100644
--- a/arch/arm/kernel/perf_event_v7.c
+++ b/arch/arm/kernel/perf_event_v7.c
@@ -736,10 +736,22 @@ static inline int armv7_pmnc_counter_has_overflowed(u32 pmnc, int idx)
 	return pmnc & BIT(ARMV7_IDX_TO_COUNTER(idx));
 }

-static inline void armv7_pmnc_select_counter(int idx)
+static inline u32 armv7_pmsel_read(void)
+{
+	u32 pmsel;
+
+	asm volatile("mrc p15, 0, %0, c9, c12, 5" : "=&r" (pmsel));
+	return pmsel;
+}
+
+static inline void armv7_pmsel_write(u32 counter)
 {
-	u32 counter = ARMV7_IDX_TO_COUNTER(idx);
 	asm volatile("mcr p15, 0, %0, c9, c12, 5" : : "r" (counter));
+}
+
+static inline void armv7_pmnc_select_counter(int idx)
+{
+	armv7_pmsel_write(ARMV7_IDX_TO_COUNTER(idx));
 	isb();
 }

@@ -952,8 +964,15 @@ static irqreturn_t armv7pmu_handle_irq(struct arm_pmu *cpu_pmu)
 	struct perf_sample_data data;
 	struct pmu_hw_events *cpuc = this_cpu_ptr(cpu_pmu->hw_events);
 	struct pt_regs *regs;
+	u32 pmsel;
 	int idx;

+
+	/*
+	 * Save pmsel in case the interrupted context was using it.
+	 */
+	pmsel = armv7_pmsel_read();
+
 	/*
 	 * Get and reset the IRQ flags
 	 */
@@ -1004,6 +1023,8 @@ static irqreturn_t armv7pmu_handle_irq(struct arm_pmu *cpu_pmu)
 	 */
 	irq_work_run();

+	armv7_pmsel_write(pmsel);
+
 	return IRQ_HANDLED;
 }

--
1.9.1

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  parent reply index

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-17  8:17 [PATCH v4 0/9] arm_pmu: Use NMI for perf interrupt Julien Thierry
2019-07-17  8:17 ` [PATCH v4 1/9] arm64: perf: avoid PMXEV* indirection Julien Thierry
2019-07-17  8:17 ` [PATCH v4 2/9] arm64: perf: Remove PMU locking Julien Thierry
2019-08-01 12:58   ` Will Deacon
2019-08-02 14:26     ` Julien Thierry
2019-07-17  8:17 ` Julien Thierry [this message]
2019-08-01 13:01   ` [PATCH v4 3/9] arm: perf: save/resore pmsel Will Deacon
2019-08-02 14:34     ` Julien Thierry
2019-07-17  8:17 ` [PATCH v4 4/9] arm: perf: Remove Remove PMU locking Julien Thierry
2019-08-01 13:06   ` Will Deacon
2019-08-02 14:36     ` Julien Thierry
2019-07-17  8:17 ` [PATCH v4 5/9] perf/arm_pmu: Move PMU lock to ARMv6 events Julien Thierry
2019-07-17  8:17 ` [PATCH v4 6/9] arm64: perf: Do not call irq_work_run in NMI context Julien Thierry
2019-08-01 13:06   ` Will Deacon
2019-08-02 14:43     ` Julien Thierry
2019-07-17  8:17 ` [PATCH v4 7/9] arm/arm64: kvm: pmu: Make overflow handler NMI safe Julien Thierry
2019-07-17  8:17 ` [PATCH v4 8/9] arm_pmu: Introduce pmu_irq_ops Julien Thierry
2019-07-17  8:17 ` [PATCH v4 9/9] arm_pmu: Use NMIs for PMU Julien Thierry
2019-07-30  9:11   ` Russell King - ARM Linux admin
2019-07-30  9:18     ` Julien Thierry
2019-07-30  9:28       ` Russell King - ARM Linux admin
2019-07-30 14:06         ` Julien Thierry
2019-07-17  9:02 ` [PATCH v4 0/9] arm_pmu: Use NMI for perf interrupt Julien Thierry
2019-07-30  9:05 ` Julien Thierry

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