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 122EBC54EBC for ; Thu, 12 Jan 2023 13:54:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233167AbjALNyd (ORCPT ); Thu, 12 Jan 2023 08:54:33 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50846 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229863AbjALNyP (ORCPT ); Thu, 12 Jan 2023 08:54:15 -0500 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 75B0F50061 for ; Thu, 12 Jan 2023 05:54:14 -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 4964613D5; Thu, 12 Jan 2023 05:54:56 -0800 (PST) Received: from FVFF77S0Q05N (unknown [10.57.43.206]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 3D08C3F67D; Thu, 12 Jan 2023 05:54:13 -0800 (PST) Date: Thu, 12 Jan 2023 13:54:10 +0000 From: Mark Rutland To: Anshuman Khandual Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon Subject: Re: [PATCH V7 3/6] arm64/perf: Add branch stack support in struct arm_pmu Message-ID: References: <20230105031039.207972-1-anshuman.khandual@arm.com> <20230105031039.207972-4-anshuman.khandual@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230105031039.207972-4-anshuman.khandual@arm.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 05, 2023 at 08:40:36AM +0530, Anshuman Khandual wrote: > This updates 'struct arm_pmu' for branch stack sampling support later. This > adds a new 'features' element in the structure to track supported features, > and another 'private' element to encapsulate implementation attributes on a > given 'struct arm_pmu'. These updates here will help in tracking any branch > stack sampling support, which is being added later. This also adds a helper > arm_pmu_branch_stack_supported(). > > This also enables perf branch stack sampling event on all 'struct arm pmu', > supporting the feature but after removing the current gate that blocks such > events unconditionally in armpmu_event_init(). Instead a quick probe can be > initiated via arm_pmu_branch_stack_supported() to ascertain the support. > > Cc: Catalin Marinas > 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.c | 3 +-- > include/linux/perf/arm_pmu.h | 9 +++++++++ > 2 files changed, 10 insertions(+), 2 deletions(-) > > diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c > index 14a3ed3bdb0b..a85b2d67022e 100644 > --- a/drivers/perf/arm_pmu.c > +++ b/drivers/perf/arm_pmu.c > @@ -510,8 +510,7 @@ static int armpmu_event_init(struct perf_event *event) > !cpumask_test_cpu(event->cpu, &armpmu->supported_cpus)) > return -ENOENT; > > - /* does not support taken branch sampling */ > - if (has_branch_stack(event)) > + if (has_branch_stack(event) && !arm_pmu_branch_stack_supported(armpmu)) > return -EOPNOTSUPP; > > return __hw_perf_event_init(event); > diff --git a/include/linux/perf/arm_pmu.h b/include/linux/perf/arm_pmu.h > index 2a9d07cee927..64e1b2594025 100644 > --- a/include/linux/perf/arm_pmu.h > +++ b/include/linux/perf/arm_pmu.h > @@ -80,11 +80,14 @@ enum armpmu_attr_groups { > ARMPMU_NR_ATTR_GROUPS > }; > > +#define ARM_PMU_BRANCH_STACK BIT(0) > + > struct arm_pmu { > struct pmu pmu; > cpumask_t supported_cpus; > char *name; > int pmuver; > + int features; > irqreturn_t (*handle_irq)(struct arm_pmu *pmu); > void (*enable)(struct perf_event *event); > void (*disable)(struct perf_event *event); Hmm, we already have the secure_access field separately. How about we fold that in and go with: unsigned int secure_access : 1, has_branch_stack : 1; ... that way we have one way to manage flags, we don't need to allocate the bits, and the bulk of the existing code for secure_access can stay as-is. > @@ -119,8 +122,14 @@ struct arm_pmu { > > /* Only to be used by ACPI probing code */ > unsigned long acpi_cpuid; > + void *private; Does this need to be on the end of struct arm_pmu, or can it be placed earlier? The line spacing makes it look like the ACPI comment applies to 'private', which isn't the case. > }; > > +static inline bool arm_pmu_branch_stack_supported(struct arm_pmu *armpmu) > +{ > + return armpmu->features & ARM_PMU_BRANCH_STACK; > +} With the above, this would become: static inline bool arm_pmu_branch_stack_supported(struct arm_pmu *armpmu) { return armpmu->has_branch_stack; } Thanks, Mark. > + > #define to_arm_pmu(p) (container_of(p, struct arm_pmu, pmu)) > > u64 armpmu_event_update(struct perf_event *event); > -- > 2.25.1 >