Messages in this thread | | | Date | Thu, 9 Jun 2022 12:32:28 +0100 | From | Will Deacon <> | Subject | Re: [PATCH V5] arm64: perf: Make exporting of pmu events configurable |
| |
[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
| |