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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 12:32:28 +0100	[thread overview]
Message-ID: <20220609113225.GA2326@willie-the-truck> (raw)
In-Reply-To: <4f5dbc00-e25b-f6ff-8585-31fc50f48a21@quicinc.com>

[Please don't top-post]

On Thu, Jun 09, 2022 at 04:05:20PM +0530, Srinivasarao Pathipati wrote:
> 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.
>
> 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.

What "Qualcomm use cases" and why should we care about them upstream?

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 12:32:28 +0100	[thread overview]
Message-ID: <20220609113225.GA2326@willie-the-truck> (raw)
In-Reply-To: <4f5dbc00-e25b-f6ff-8585-31fc50f48a21@quicinc.com>

[Please don't top-post]

On Thu, Jun 09, 2022 at 04:05:20PM +0530, Srinivasarao Pathipati wrote:
> 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.
>
> 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.

What "Qualcomm use cases" and why should we care about them upstream?

Will

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  reply	other threads:[~2022-06-09 11:36 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 [this message]
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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