Re: [PATCH V5] arm64: perf: Make exporting of pmu events configurable

[Srinivasarao Pathipati]

On 6/9/2022 5:02 PM, Will Deacon wrote:
> [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@xxxxxxxxxxx>
> > > > ---
> > > > 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?

Thanks Will & Robin for your inputs .

Understood your point ,  pushed next version [V6] after removing kernel 
parameters code.

> Will