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 19B16C433EF for ; Thu, 10 Mar 2022 10:21:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241162AbiCJKWM (ORCPT ); Thu, 10 Mar 2022 05:22:12 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35968 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232377AbiCJKWJ (ORCPT ); Thu, 10 Mar 2022 05:22:09 -0500 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 7F3A013DE15; Thu, 10 Mar 2022 02:21:08 -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 3ABEB1650; Thu, 10 Mar 2022 02:21:08 -0800 (PST) Received: from [10.57.41.41] (unknown [10.57.41.41]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2620A3FA27; Thu, 10 Mar 2022 02:21:04 -0800 (PST) Message-ID: <6dc9a4e5-8f74-dfb5-d9f6-60e9d6b65146@arm.com> Date: Thu, 10 Mar 2022 10:21:03 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: [PATCH V2 4/8] perf: Capture branch privilege information Content-Language: en-US To: Anshuman Khandual , linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, peterz@infradead.org, acme@kernel.org Cc: suzuki.poulose@arm.com, Ingo Molnar , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Thomas Gleixner , Will Deacon , linux-arm-kernel@lists.infradead.org References: <20220309033642.144769-1-anshuman.khandual@arm.com> <20220309033642.144769-5-anshuman.khandual@arm.com> From: James Clark In-Reply-To: <20220309033642.144769-5-anshuman.khandual@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/03/2022 03:36, Anshuman Khandual wrote: > Platforms like arm64 could capture privilege level information for all the > branch records. Hence this adds a new element in the struct branch_entry to > record the privilege level information, which could be requested through a > new event.attr.branch_sample_type based flag PERF_SAMPLE_BRANCH_PRIV_SAVE. > This flag helps user choose whether privilege information is captured. > > Cc: Peter Zijlstra > Cc: Ingo Molnar > Cc: Arnaldo Carvalho de Melo > Cc: Mark Rutland > Cc: Alexander Shishkin > Cc: Jiri Olsa > Cc: Namhyung Kim > Cc: Thomas Gleixner > Cc: Will Deacon > Cc: linux-arm-kernel@lists.infradead.org > Cc: linux-perf-users@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > Signed-off-by: Anshuman Khandual > --- > include/uapi/linux/perf_event.h | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) > > diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h > index d29280adc3c4..0e96e2017f68 100644 > --- a/include/uapi/linux/perf_event.h > +++ b/include/uapi/linux/perf_event.h > @@ -204,6 +204,8 @@ enum perf_branch_sample_type_shift { > > PERF_SAMPLE_BRANCH_HW_INDEX_SHIFT = 17, /* save low level index of raw branch records */ > > + PERF_SAMPLE_BRANCH_PRIV_SAVE_SHIFT = 18, /* save privillege mode */ > + > PERF_SAMPLE_BRANCH_MAX_SHIFT /* non-ABI */ > }; > > @@ -233,6 +235,8 @@ enum perf_branch_sample_type { > > PERF_SAMPLE_BRANCH_HW_INDEX = 1U << PERF_SAMPLE_BRANCH_HW_INDEX_SHIFT, > > + PERF_SAMPLE_BRANCH_PRIV_SAVE = 1U << PERF_SAMPLE_BRANCH_PRIV_SAVE_SHIFT, > + > PERF_SAMPLE_BRANCH_MAX = 1U << PERF_SAMPLE_BRANCH_MAX_SHIFT, > }; > > @@ -271,6 +275,12 @@ enum { > PERF_BR_NEW_MAX, > }; > > +enum { > + PERF_BR_USER = 0, > + PERF_BR_KERNEL = 1, > + PERF_BR_HV = 2, > +}; 0 should be "PERF_BR_PRIV_UNKNOWN" so userspace knows if it was not enabled otherwise it will look like all samples are PERF_BR_USER when actually priv type recording was just disabled. I think it's not even always possible to go backwards from a sample to work out what the event attributes were so this can be interpreted (taking all of perf script and every corner case into account). Starting at 0=UNKNOWN is consistent with the other fields and makes parsing it a whole lot easier. James > + > #define PERF_SAMPLE_BRANCH_PLM_ALL \ > (PERF_SAMPLE_BRANCH_USER|\ > PERF_SAMPLE_BRANCH_KERNEL|\ > @@ -1386,7 +1396,8 @@ struct perf_branch_entry { > cycles:16, /* cycle count to last branch */ > type:4, /* branch type */ > new_type:4, /* additional branch type */ > - reserved:36; > + priv:2, /* privilege level */ > + reserved:34; > }; > > union perf_sample_weight {