From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C77CBC4332F for ; Fri, 18 Nov 2022 18:01:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241913AbiKRSBZ (ORCPT ); Fri, 18 Nov 2022 13:01:25 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48948 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234073AbiKRSBW (ORCPT ); Fri, 18 Nov 2022 13:01:22 -0500 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id B438F2CC96; Fri, 18 Nov 2022 10:01:20 -0800 (PST) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id C6C9423A; Fri, 18 Nov 2022 10:01:17 -0800 (PST) Received: from FVFF77S0Q05N.cambridge.arm.com (FVFF77S0Q05N.cambridge.arm.com [10.1.34.127]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 993613F663; Fri, 18 Nov 2022 10:01:09 -0800 (PST) Date: Fri, 18 Nov 2022 18:01:06 +0000 From: Mark Rutland To: Anshuman Khandual Cc: linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-arm-kernel@lists.infradead.org, peterz@infradead.org, acme@kernel.org, will@kernel.org, catalin.marinas@arm.com, Mark Brown , James Clark , Rob Herring , Marc Zyngier , Suzuki Poulose , Ingo Molnar Subject: Re: [PATCH V5 4/7] driver/perf/arm_pmu_platform: Add support for BRBE attributes detection Message-ID: References: <20221107062514.2851047-1-anshuman.khandual@arm.com> <20221107062514.2851047-5-anshuman.khandual@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221107062514.2851047-5-anshuman.khandual@arm.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 07, 2022 at 11:55:11AM +0530, Anshuman Khandual wrote: > This adds arm pmu infrastrure to probe BRBE implementation's attributes via > driver exported callbacks later. The actual BRBE feature detection will be > added by the driver itself. > > CPU specific BRBE entries, cycle count, format support gets detected during > PMU init. This information gets saved in per-cpu struct pmu_hw_events which > later helps in operating BRBE during a perf event context. Do we expect this to vary between CPUs handled by the same struct arm_pmu ? > Cc: Will Deacon > Cc: Mark Rutland > Cc: linux-arm-kernel@lists.infradead.org > Cc: linux-kernel@vger.kernel.org > Signed-off-by: Anshuman Khandual > --- > drivers/perf/arm_pmu_platform.c | 34 +++++++++++++++++++++++++++++++++ > 1 file changed, 34 insertions(+) > > diff --git a/drivers/perf/arm_pmu_platform.c b/drivers/perf/arm_pmu_platform.c > index 933b96e243b8..acdc445081aa 100644 > --- a/drivers/perf/arm_pmu_platform.c > +++ b/drivers/perf/arm_pmu_platform.c > @@ -172,6 +172,36 @@ static int armpmu_request_irqs(struct arm_pmu *armpmu) > return err; > } > > +static void arm_brbe_probe_cpu(void *info) > +{ > + struct pmu_hw_events *hw_events; > + struct arm_pmu *armpmu = info; > + > + /* > + * Return from here, if BRBE driver has not been > + * implemented for this PMU. This helps prevent > + * kernel crash later when brbe_probe() will be > + * called on the PMU. > + */ > + if (!armpmu->brbe_probe) > + return; Since this is a field on struct arm_pmu, why doesn't armpmu_request_brbe() check this before calling smp_call_function_single(), to avoid the redundant IPI? > + > + hw_events = per_cpu_ptr(armpmu->hw_events, smp_processor_id()); > + armpmu->brbe_probe(hw_events); > +} > + > +static int armpmu_request_brbe(struct arm_pmu *armpmu) > +{ > + int cpu, err = 0; > + > + for_each_cpu(cpu, &armpmu->supported_cpus) { > + err = smp_call_function_single(cpu, arm_brbe_probe_cpu, armpmu, 1); Why does this need to be called on each CPU in the supported_cpus mask? I don't see anything here to handle late hotplug, so this looks suspicious. Either we're missing something, or it's redundant at boot time. Thanks, Mark. > + if (err) > + return err; > + } > + return err; > +} > + > static void armpmu_free_irqs(struct arm_pmu *armpmu) > { > int cpu; > @@ -229,6 +259,10 @@ int arm_pmu_device_probe(struct platform_device *pdev, > if (ret) > goto out_free_irqs; > > + ret = armpmu_request_brbe(pmu); > + if (ret) > + goto out_free_irqs; > + > ret = armpmu_register(pmu); > if (ret) { > dev_err(dev, "failed to register PMU devices!\n"); > -- > 2.25.1 >