Hi Greg,
Following the conversation with Marc, we discovered that an important fix for ARM PMU is not backported to 4.14.y tree, it affects counter value and give out nonsensical result.
Can you please include the following commit? ``` commit 3cce50dfec4a5b0414c974190940f47dd32c6dee Author: Suzuki K Poulose suzuki.poulose@arm.com Date: Tue Jul 10 09:58:03 2018 +0100
arm64: perf: Disable PMU while processing counter overflows
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@arm.com Cc: Will Deacon will.deacon@arm.com Acked-by: Mark Rutland mark.rutland@arm.com Signed-off-by: Suzuki K Poulose suzuki.poulose@arm.com Signed-off-by: Will Deacon will.deacon@arm.com ```
For more details:
https://lists.cs.columbia.edu/pipermail/kvmarm/2021-June/047471.html
Regards, Aman Priyadarshi
Amazon Development Center Germany GmbH Krausenstr. 38 10117 Berlin Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B Sitz: Berlin Ust-ID: DE 289 237 879
On Wed, Jun 16, 2021 at 01:09:49PM +0200, Aman Priyadarshi wrote:
Hi Greg,
Following the conversation with Marc, we discovered that an important fix for ARM PMU is not backported to 4.14.y tree, it affects counter value and give out nonsensical result.
Can you please include the following commit?
commit 3cce50dfec4a5b0414c974190940f47dd32c6dee Author: Suzuki K Poulose <suzuki.poulose@arm.com> Date: Tue Jul 10 09:58:03 2018 +0100 arm64: perf: Disable PMU while processing counter overflows 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@arm.com> Cc: Will Deacon <will.deacon@arm.com> Acked-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com>
It does not apply cleanly so you will have to provide a working backport for us.
For more details:
https://lists.cs.columbia.edu/pipermail/kvmarm/2021-June/047471.html
lore.kernel.org is your friend :)
thanks,
greg k-h
From: Suzuki K Poulose suzuki.poulose@arm.com
[ Upstream commit 3cce50dfec4a5b0414c974190940f47dd32c6dee ]
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@arm.com Cc: Will Deacon will.deacon@arm.com Acked-by: Mark Rutland mark.rutland@arm.com Signed-off-by: Suzuki K Poulose suzuki.poulose@arm.com Signed-off-by: Will Deacon will.deacon@arm.com Signed-off-by: Aman Priyadarshi apeureka@amazon.de Cc: stable@vger.kernel.org --- arch/arm64/kernel/perf_event.c | 50 +++++++++++++++++++--------------- 1 file changed, 28 insertions(+), 22 deletions(-)
diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c index 53df84b2a07f..4ee1228d29eb 100644 --- a/arch/arm64/kernel/perf_event.c +++ b/arch/arm64/kernel/perf_event.c @@ -670,6 +670,28 @@ static void armv8pmu_disable_event(struct perf_event *event) 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(int irq_num, void *dev) */ 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(int irq_num, void *dev) 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(int irq_num, void *dev) 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) {
On Wed, Jun 16, 2021 at 09:28:59PM +0200, Aman Priyadarshi wrote:
From: Suzuki K Poulose suzuki.poulose@arm.com
[ Upstream commit 3cce50dfec4a5b0414c974190940f47dd32c6dee ]
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@arm.com Cc: Will Deacon will.deacon@arm.com Acked-by: Mark Rutland mark.rutland@arm.com Signed-off-by: Suzuki K Poulose suzuki.poulose@arm.com Signed-off-by: Will Deacon will.deacon@arm.com Signed-off-by: Aman Priyadarshi apeureka@amazon.de Cc: stable@vger.kernel.org
arch/arm64/kernel/perf_event.c | 50 +++++++++++++++++++--------------- 1 file changed, 28 insertions(+), 22 deletions(-)
What stable tree(s) do you want this applied to?
thanks,
greg k-h
On Thu, 17 Jun 2021 05:51:03 +0100, Greg Kroah-Hartman gregkh@linuxfoundation.org wrote:
On Wed, Jun 16, 2021 at 09:28:59PM +0200, Aman Priyadarshi wrote:
From: Suzuki K Poulose suzuki.poulose@arm.com
[ Upstream commit 3cce50dfec4a5b0414c974190940f47dd32c6dee ]
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@arm.com Cc: Will Deacon will.deacon@arm.com Acked-by: Mark Rutland mark.rutland@arm.com Signed-off-by: Suzuki K Poulose suzuki.poulose@arm.com Signed-off-by: Will Deacon will.deacon@arm.com Signed-off-by: Aman Priyadarshi apeureka@amazon.de Cc: stable@vger.kernel.org
arch/arm64/kernel/perf_event.c | 50 +++++++++++++++++++--------------- 1 file changed, 28 insertions(+), 22 deletions(-)
What stable tree(s) do you want this applied to?
I guess that'd be 4.14 and previous stables if the patch actually applies.
Thanks,
M.
On Thu, 2021-06-17 at 08:34 +0100, Marc Zyngier wrote:
CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you can confirm the sender and know the content is safe.
On Thu, 17 Jun 2021 05:51:03 +0100, Greg Kroah-Hartman gregkh@linuxfoundation.org wrote:
On Wed, Jun 16, 2021 at 09:28:59PM +0200, Aman Priyadarshi wrote:
From: Suzuki K Poulose suzuki.poulose@arm.com
[ Upstream commit 3cce50dfec4a5b0414c974190940f47dd32c6dee ]
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@arm.com Cc: Will Deacon will.deacon@arm.com Acked-by: Mark Rutland mark.rutland@arm.com Signed-off-by: Suzuki K Poulose suzuki.poulose@arm.com Signed-off-by: Will Deacon will.deacon@arm.com Signed-off-by: Aman Priyadarshi apeureka@amazon.de Cc: stable@vger.kernel.org
arch/arm64/kernel/perf_event.c | 50 +++++++++++++++++++-------------
1 file changed, 28 insertions(+), 22 deletions(-)
What stable tree(s) do you want this applied to?
I guess that'd be 4.14 and previous stables if the patch actually applies.
Correct. I have tested the patch on 4.14.y, can confirm that it applies cleanly on 4.9.y as well.
Thanks, Aman Priyadarshi
Amazon Development Center Germany GmbH Krausenstr. 38 10117 Berlin Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B Sitz: Berlin Ust-ID: DE 289 237 879
On Thu, Jun 17, 2021 at 10:57:00AM +0200, Aman Priyadarshi wrote:
On Thu, 2021-06-17 at 08:34 +0100, Marc Zyngier wrote:
CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you can confirm the sender and know the content is safe.
On Thu, 17 Jun 2021 05:51:03 +0100, Greg Kroah-Hartman gregkh@linuxfoundation.org wrote:
On Wed, Jun 16, 2021 at 09:28:59PM +0200, Aman Priyadarshi wrote:
From: Suzuki K Poulose suzuki.poulose@arm.com
[ Upstream commit 3cce50dfec4a5b0414c974190940f47dd32c6dee ]
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@arm.com Cc: Will Deacon will.deacon@arm.com Acked-by: Mark Rutland mark.rutland@arm.com Signed-off-by: Suzuki K Poulose suzuki.poulose@arm.com Signed-off-by: Will Deacon will.deacon@arm.com Signed-off-by: Aman Priyadarshi apeureka@amazon.de Cc: stable@vger.kernel.org
arch/arm64/kernel/perf_event.c | 50 +++++++++++++++++++-------------
1 file changed, 28 insertions(+), 22 deletions(-)
What stable tree(s) do you want this applied to?
I guess that'd be 4.14 and previous stables if the patch actually applies.
Correct. I have tested the patch on 4.14.y, can confirm that it applies cleanly on 4.9.y as well.
Now queued up, thanks.
greg k-h
linux-stable-mirror@lists.linaro.org
-
Aman Priyadarshi -
Greg Kroah-Hartman -
Marc Zyngier