From: Robin Murphy <robin.murphy@arm.com> To: Srinivasarao Pathipati <quic_c_spathi@quicinc.com>, Will Deacon <will@kernel.org> Cc: mark.rutland@arm.com, peterz@infradead.org, mingo@redhat.com, acme@kernel.org, alexander.shishkin@linux.intel.com, jolsa@kernel.org, namhyung@kernel.org, catalin.marinas@arm.com, linux-arm-kernel@lists.infradead.org, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH V5] arm64: perf: Make exporting of pmu events configurable Date: Thu, 9 Jun 2022 12:36:50 +0100 [thread overview] Message-ID: <a0b03913-6412-0e2a-d9c5-431c52ff624f@arm.com> (raw) In-Reply-To: <4f5dbc00-e25b-f6ff-8585-31fc50f48a21@quicinc.com> On 2022-06-09 11:35, Srinivasarao Pathipati wrote: > On our Qualcomm platforms, The X bit is getting set by firmware at early > bootup for Qualcomm use cases > and non-secure world is resetting it, that causing issue. I think you're going to have to clarify what exactly this "issue" is if we're ever going to make sense of it... I can't imagine that export from a disabled PMU would matter much, so my best guess is that EL2 firmware has reserved some counters via MDCR_EL2.HPMN which it's using to monitor the Non-Secure boot; if that also depends on PMCR.X remaining set, then as far as I can see it's really the firmware's own stupid fault for not using MDCR_EL2.TPMCR to prevent Linux from messing with its configuration. Or maybe something in the Secure world is trying to use the PMU independently and it's an EL3 bug where PMCR_EL0 isn't being context-switched properly? Robin. > On 6/9/2022 3:32 PM, Will Deacon wrote: >> On Mon, May 23, 2022 at 05:19:34PM +0530, Srinivasarao Pathipati wrote: >>> The PMU export bit (PMCR_EL0.X) is getting reset during pmu reset, >>> Make is configurable using sysctls to enable/disable at runtime. >>> It can also be enabled at early bootup with kernel arguments. >>> >>> Signed-off-by: Srinivasarao Pathipati <quic_c_spathi@quicinc.com> >>> --- >>> Changes since V4: >>> - Registering sysctls dynamically for only arm64 as suggested by >>> Will >>> - Not removed the code to configure with kernel parameters >>> as the sysctl's kernel parameter(sysctl.kernel.export_pmu_events) >>> is not working at early bootup. pmu_reset() getting called before >>> sysctl's kernel parameter is set. >> Why do you need this during early bootup? Perf won't program any events >> until much later and if somebody else is configuring the PMU before >> entering Linux then they can also set that X bit in the PMCR. >> >> Will > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
WARNING: multiple messages have this Message-ID (diff)
From: Robin Murphy <robin.murphy@arm.com> To: Srinivasarao Pathipati <quic_c_spathi@quicinc.com>, Will Deacon <will@kernel.org> Cc: mark.rutland@arm.com, peterz@infradead.org, mingo@redhat.com, acme@kernel.org, alexander.shishkin@linux.intel.com, jolsa@kernel.org, namhyung@kernel.org, catalin.marinas@arm.com, linux-arm-kernel@lists.infradead.org, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH V5] arm64: perf: Make exporting of pmu events configurable Date: Thu, 9 Jun 2022 12:36:50 +0100 [thread overview] Message-ID: <a0b03913-6412-0e2a-d9c5-431c52ff624f@arm.com> (raw) In-Reply-To: <4f5dbc00-e25b-f6ff-8585-31fc50f48a21@quicinc.com> On 2022-06-09 11:35, Srinivasarao Pathipati wrote: > On our Qualcomm platforms, The X bit is getting set by firmware at early > bootup for Qualcomm use cases > and non-secure world is resetting it, that causing issue. I think you're going to have to clarify what exactly this "issue" is if we're ever going to make sense of it... I can't imagine that export from a disabled PMU would matter much, so my best guess is that EL2 firmware has reserved some counters via MDCR_EL2.HPMN which it's using to monitor the Non-Secure boot; if that also depends on PMCR.X remaining set, then as far as I can see it's really the firmware's own stupid fault for not using MDCR_EL2.TPMCR to prevent Linux from messing with its configuration. Or maybe something in the Secure world is trying to use the PMU independently and it's an EL3 bug where PMCR_EL0 isn't being context-switched properly? Robin. > On 6/9/2022 3:32 PM, Will Deacon wrote: >> On Mon, May 23, 2022 at 05:19:34PM +0530, Srinivasarao Pathipati wrote: >>> The PMU export bit (PMCR_EL0.X) is getting reset during pmu reset, >>> Make is configurable using sysctls to enable/disable at runtime. >>> It can also be enabled at early bootup with kernel arguments. >>> >>> Signed-off-by: Srinivasarao Pathipati <quic_c_spathi@quicinc.com> >>> --- >>> Changes since V4: >>> - Registering sysctls dynamically for only arm64 as suggested by >>> Will >>> - Not removed the code to configure with kernel parameters >>> as the sysctl's kernel parameter(sysctl.kernel.export_pmu_events) >>> is not working at early bootup. pmu_reset() getting called before >>> sysctl's kernel parameter is set. >> Why do you need this during early bootup? Perf won't program any events >> until much later and if somebody else is configuring the PMU before >> entering Linux then they can also set that X bit in the PMCR. >> >> Will > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2022-06-09 11:37 UTC|newest] Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-05-23 11:49 [PATCH V5] arm64: perf: Make exporting of pmu events configurable Srinivasarao Pathipati 2022-05-23 11:49 ` Srinivasarao Pathipati 2022-06-09 5:02 ` Srinivasarao Pathipati 2022-06-09 5:02 ` Srinivasarao Pathipati 2022-06-09 10:02 ` Will Deacon 2022-06-09 10:02 ` Will Deacon 2022-06-09 10:35 ` Srinivasarao Pathipati 2022-06-09 10:35 ` Srinivasarao Pathipati 2022-06-09 11:32 ` Will Deacon 2022-06-09 11:32 ` Will Deacon 2022-06-09 13:07 ` Srinivasarao Pathipati 2022-06-09 13:07 ` Srinivasarao Pathipati 2022-06-09 11:36 ` Robin Murphy [this message] 2022-06-09 11:36 ` Robin Murphy
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