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 80195C433FE for ; Fri, 11 Mar 2022 03:25:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345967AbiCKD0t (ORCPT ); Thu, 10 Mar 2022 22:26:49 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37618 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345934AbiCKD0p (ORCPT ); Thu, 10 Mar 2022 22:26:45 -0500 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id AB7BBC5D8F; Thu, 10 Mar 2022 19:25:42 -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 205A514BF; Thu, 10 Mar 2022 19:25:42 -0800 (PST) Received: from [10.163.34.78] (unknown [10.163.34.78]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9704D3F7D8; Thu, 10 Mar 2022 19:25:37 -0800 (PST) Message-ID: Date: Fri, 11 Mar 2022 08:55:36 +0530 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: James Clark , 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> <6dc9a4e5-8f74-dfb5-d9f6-60e9d6b65146@arm.com> From: Anshuman Khandual In-Reply-To: <6dc9a4e5-8f74-dfb5-d9f6-60e9d6b65146@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 3/10/22 15:51, James Clark wrote: > > > 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. Makes sense. > > 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. Fair enough, will start the enum with PERF_BR_PRIV_UNKNOWN and expand the field 'perf_branch_entry.priv' to 3 bits instead, in order to accommodate any future needs regarding other captured privilege levels. > > 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 {