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 CF3A1C54EBE for ; Fri, 13 Jan 2023 04:21:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232905AbjAMEVD (ORCPT ); Thu, 12 Jan 2023 23:21:03 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41666 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231429AbjAMEUG (ORCPT ); Thu, 12 Jan 2023 23:20:06 -0500 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 3686B66986 for ; Thu, 12 Jan 2023 20:15:28 -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 BD6B2FEC; Thu, 12 Jan 2023 20:16:10 -0800 (PST) Received: from [10.162.41.9] (unknown [10.162.41.9]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8C6133F587; Thu, 12 Jan 2023 20:15:26 -0800 (PST) Message-ID: <0351f0bc-d94b-957f-8e03-6525e47d63a4@arm.com> Date: Fri, 13 Jan 2023 09:45:22 +0530 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.2.2 Subject: Re: [PATCH V7 3/6] arm64/perf: Add branch stack support in struct arm_pmu Content-Language: en-US To: Mark Rutland Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon References: <20230105031039.207972-1-anshuman.khandual@arm.com> <20230105031039.207972-4-anshuman.khandual@arm.com> From: Anshuman Khandual In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/12/23 19:24, Mark Rutland wrote: > 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; Something like this would work, but should we use __u32 instead of unsigned int to ensure 32 bit width ? - bool secure_access; /* 32-bit ARM only */ + unsigned int secure_access : 1, /* 32-bit ARM only */ + has_branch_stack: 1, + reserved : 31; > > ... 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. Right, the changed code also builds on arm32 without any code change. > >> @@ -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? This additional 'private' attribute structure sticking out from struct arm_pmu should be at the end. But is there any benefit moving this earlier ? > > The line spacing makes it look like the ACPI comment applies to 'private', > which isn't the case. Sure, will add the following comment, and a space in between. diff --git a/include/linux/perf/arm_pmu.h b/include/linux/perf/arm_pmu.h index f60f7e01acae..c0a090ff7991 100644 --- a/include/linux/perf/arm_pmu.h +++ b/include/linux/perf/arm_pmu.h @@ -130,6 +130,8 @@ struct arm_pmu { /* Only to be used by ACPI probing code */ unsigned long acpi_cpuid; + + /* Implementation specific attributes */ void *private; }; > >> }; >> >> +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; > } Right, will change this helper as required.