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From: Will Deacon <will@kernel.org>
To: Srinivasarao Pathipati <quic_c_spathi@quicinc.com>
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 11:02:47 +0100	[thread overview]
Message-ID: <20220609100247.GA2187@willie-the-truck> (raw)
In-Reply-To: <1653306574-20946-1-git-send-email-quic_c_spathi@quicinc.com>

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

WARNING: multiple messages have this Message-ID (diff)
From: Will Deacon <will@kernel.org>
To: Srinivasarao Pathipati <quic_c_spathi@quicinc.com>
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 11:02:47 +0100	[thread overview]
Message-ID: <20220609100247.GA2187@willie-the-truck> (raw)
In-Reply-To: <1653306574-20946-1-git-send-email-quic_c_spathi@quicinc.com>

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

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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  parent reply	other threads:[~2022-06-09 10:02 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 [this message]
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
2022-06-09 11:36       ` Robin Murphy

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