This is a note to let you know that I've just added the patch titled
arm64: perf: Disable PMU while processing counter overflows
to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
arm64-perf-disable-pmu-while-processing-counter-overflows.patch
and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 3cce50dfec4a5b0414c974190940f47dd32c6dee Mon Sep 17 00:00:00 2001
From: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
Date: Tue, 10 Jul 2018 09:58:03 +0100
Subject: arm64: perf: Disable PMU while processing counter overflows
From: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
commit 3cce50dfec4a5b0414c974190940f47dd32c6dee upstream.
The arm64 PMU updates the event counters and reprograms the
counters in the overflow IRQ handler without disabling the
PMU. This could potentially cause skews in for group counters,
where the overflowed counters may potentially loose some event
counts, while they are reprogrammed. To prevent this, disable
the PMU while we process the counter overflows and enable it
right back when we are done.
This patch also moves the PMU stop/start routines to avoid a
forward declaration.
Suggested-by: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Acked-by: Mark Rutland <mark.rutland@xxxxxxx>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Aman Priyadarshi <apeureka@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arm64/kernel/perf_event.c | 50 ++++++++++++++++++++++-------------------
1 file changed, 28 insertions(+), 22 deletions(-)
--- a/arch/arm64/kernel/perf_event.c
+++ b/arch/arm64/kernel/perf_event.c
@@ -670,6 +670,28 @@ static void armv8pmu_disable_event(struc
raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
}
+static void armv8pmu_start(struct arm_pmu *cpu_pmu)
+{
+ unsigned long flags;
+ struct pmu_hw_events *events = this_cpu_ptr(cpu_pmu->hw_events);
+
+ raw_spin_lock_irqsave(&events->pmu_lock, flags);
+ /* Enable all counters */
+ armv8pmu_pmcr_write(armv8pmu_pmcr_read() | ARMV8_PMU_PMCR_E);
+ raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
+}
+
+static void armv8pmu_stop(struct arm_pmu *cpu_pmu)
+{
+ unsigned long flags;
+ struct pmu_hw_events *events = this_cpu_ptr(cpu_pmu->hw_events);
+
+ raw_spin_lock_irqsave(&events->pmu_lock, flags);
+ /* Disable all counters */
+ armv8pmu_pmcr_write(armv8pmu_pmcr_read() & ~ARMV8_PMU_PMCR_E);
+ raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
+}
+
static irqreturn_t armv8pmu_handle_irq(int irq_num, void *dev)
{
u32 pmovsr;
@@ -695,6 +717,11 @@ static irqreturn_t armv8pmu_handle_irq(i
*/
regs = get_irq_regs();
+ /*
+ * Stop the PMU while processing the counter overflows
+ * to prevent skews in group events.
+ */
+ armv8pmu_stop(cpu_pmu);
for (idx = 0; idx < cpu_pmu->num_events; ++idx) {
struct perf_event *event = cpuc->events[idx];
struct hw_perf_event *hwc;
@@ -719,6 +746,7 @@ static irqreturn_t armv8pmu_handle_irq(i
if (perf_event_overflow(event, &data, regs))
cpu_pmu->disable(event);
}
+ armv8pmu_start(cpu_pmu);
/*
* Handle the pending perf events.
@@ -732,28 +760,6 @@ static irqreturn_t armv8pmu_handle_irq(i
return IRQ_HANDLED;
}
-static void armv8pmu_start(struct arm_pmu *cpu_pmu)
-{
- unsigned long flags;
- struct pmu_hw_events *events = this_cpu_ptr(cpu_pmu->hw_events);
-
- raw_spin_lock_irqsave(&events->pmu_lock, flags);
- /* Enable all counters */
- armv8pmu_pmcr_write(armv8pmu_pmcr_read() | ARMV8_PMU_PMCR_E);
- raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
-}
-
-static void armv8pmu_stop(struct arm_pmu *cpu_pmu)
-{
- unsigned long flags;
- struct pmu_hw_events *events = this_cpu_ptr(cpu_pmu->hw_events);
-
- raw_spin_lock_irqsave(&events->pmu_lock, flags);
- /* Disable all counters */
- armv8pmu_pmcr_write(armv8pmu_pmcr_read() & ~ARMV8_PMU_PMCR_E);
- raw_spin_unlock_irqrestore(&events->pmu_lock, flags);
-}
-
static int armv8pmu_get_event_idx(struct pmu_hw_events *cpuc,
struct perf_event *event)
{
Patches currently in stable-queue which might be from suzuki.poulose@xxxxxxx are
queue-4.14/arm64-perf-disable-pmu-while-processing-counter-overflows.patch
