Messages in this thread | | | Date | Thu, 9 Jun 2022 12:36:50 +0100 | Subject | Re: [PATCH V5] arm64: perf: Make exporting of pmu events configurable | From | Robin Murphy <> |
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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
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