* [PATCH V2] arm64: perf: Retain PMCR.X of PMCR_EL0 during reset
@ 2022-04-29 11:29 Srinivasarao Pathipati
2022-05-06 14:12 ` Will Deacon
0 siblings, 1 reply; 3+ messages in thread
From: Srinivasarao Pathipati @ 2022-04-29 11:29 UTC (permalink / raw)
To: will, mark.rutland, peterz, mingo, acme, alexander.shishkin,
jolsa, namhyung, catalin.marinas, linux-arm-kernel,
linux-perf-users, linux-kernel
Cc: Srinivasarao Pathipati
Preserve the bit PMCR.X of PMCR_EL0 during PMU reset to export
PMU events. as it could be set before PMU initialization.
Signed-off-by: Srinivasarao Pathipati <quic_c_spathi@quicinc.com>
---
Changes since V1:
- Preserving only PMCR_X bit as per Robin Murphy's comment
---
arch/arm64/kernel/perf_event.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c
index cb69ff1..532a417 100644
--- a/arch/arm64/kernel/perf_event.c
+++ b/arch/arm64/kernel/perf_event.c
@@ -1047,6 +1047,9 @@ static void armv8pmu_reset(void *info)
if (armv8pmu_has_long_event(cpu_pmu))
pmcr |= ARMV8_PMU_PMCR_LP;
+ /* Preserve PMCR_X to export PMU events */
+ pmcr |= (armv8pmu_pmcr_read() & ARMV8_PMU_PMCR_X);
+
armv8pmu_pmcr_write(pmcr);
}
--
2.7.4
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH V2] arm64: perf: Retain PMCR.X of PMCR_EL0 during reset
2022-04-29 11:29 [PATCH V2] arm64: perf: Retain PMCR.X of PMCR_EL0 during reset Srinivasarao Pathipati
@ 2022-05-06 14:12 ` Will Deacon
2022-05-09 13:21 ` Srinivasarao Pathipati
0 siblings, 1 reply; 3+ messages in thread
From: Will Deacon @ 2022-05-06 14:12 UTC (permalink / raw)
To: Srinivasarao Pathipati
Cc: mark.rutland, peterz, mingo, acme, alexander.shishkin, jolsa,
namhyung, catalin.marinas, linux-arm-kernel, linux-perf-users,
linux-kernel
On Fri, Apr 29, 2022 at 04:59:09PM +0530, Srinivasarao Pathipati wrote:
> Preserve the bit PMCR.X of PMCR_EL0 during PMU reset to export
> PMU events. as it could be set before PMU initialization.
>
> Signed-off-by: Srinivasarao Pathipati <quic_c_spathi@quicinc.com>
> ---
> Changes since V1:
> - Preserving only PMCR_X bit as per Robin Murphy's comment
> ---
> arch/arm64/kernel/perf_event.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c
> index cb69ff1..532a417 100644
> --- a/arch/arm64/kernel/perf_event.c
> +++ b/arch/arm64/kernel/perf_event.c
> @@ -1047,6 +1047,9 @@ static void armv8pmu_reset(void *info)
> if (armv8pmu_has_long_event(cpu_pmu))
> pmcr |= ARMV8_PMU_PMCR_LP;
>
> + /* Preserve PMCR_X to export PMU events */
> + pmcr |= (armv8pmu_pmcr_read() & ARMV8_PMU_PMCR_X);
I don't think this should be unconditional. Exporting events could easily
result in additional power consumption, and potentially even hardware
lockups.
Please stick this behind something like a sysctl toggle or sysfs control,
with documentation about what it does. It should default to disabled.
Will
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH V2] arm64: perf: Retain PMCR.X of PMCR_EL0 during reset
2022-05-06 14:12 ` Will Deacon
@ 2022-05-09 13:21 ` Srinivasarao Pathipati
0 siblings, 0 replies; 3+ messages in thread
From: Srinivasarao Pathipati @ 2022-05-09 13:21 UTC (permalink / raw)
To: Will Deacon
Cc: mark.rutland, peterz, mingo, acme, alexander.shishkin, jolsa,
namhyung, catalin.marinas, linux-arm-kernel, linux-perf-users,
linux-kernel
Thanks Will for reviewing patch
We are seeing issue at early boot up , so we will make this configurable
with kernel arguments and push
On 5/6/2022 7:42 PM, Will Deacon wrote:
> Changes since V1:
> - Preserving only PMCR_X bit as per Robin Murphy's comment
^ permalink raw reply [flat|nested] 3+ messages in thread
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2022-04-29 11:29 [PATCH V2] arm64: perf: Retain PMCR.X of PMCR_EL0 during reset Srinivasarao Pathipati
2022-05-06 14:12 ` Will Deacon
2022-05-09 13:21 ` Srinivasarao Pathipati
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