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 EC372C433F5 for ; Fri, 28 Jan 2022 11:19:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348149AbiA1LTo (ORCPT ); Fri, 28 Jan 2022 06:19:44 -0500 Received: from foss.arm.com ([217.140.110.172]:37426 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348131AbiA1LTg (ORCPT ); Fri, 28 Jan 2022 06:19:36 -0500 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 DD95B113E; Fri, 28 Jan 2022 03:19:32 -0800 (PST) Received: from [10.57.86.86] (unknown [10.57.86.86]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 5E7163F766; Fri, 28 Jan 2022 03:19:30 -0800 (PST) Message-ID: Date: Fri, 28 Jan 2022 11:19:28 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Thunderbird/91.5.1 Subject: Re: [PATCH v2 1/6] coresight: Add config flag to enable branch broadcast To: James Clark , mathieu.poirier@linaro.org, coresight@lists.linaro.org, leo.yan@linaro.com, mike.leach@linaro.org Cc: Leo Yan , John Garry , Will Deacon , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org References: <20220113091056.1297982-1-james.clark@arm.com> <20220113091056.1297982-2-james.clark@arm.com> From: Suzuki K Poulose In-Reply-To: <20220113091056.1297982-2-james.clark@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 13/01/2022 09:10, James Clark wrote: > When enabled, all taken branch addresses are output, even if the branch > was because of a direct branch instruction. This enables reconstruction > of the program flow without having access to the memory image of the > code being executed. > > Use bit 8 for the config option which would be the correct bit for > programming ETMv3. Although branch broadcast can't be enabled on ETMv3 > because it's not in the define ETM3X_SUPPORTED_OPTIONS, using the > correct bit might help prevent future collisions or allow it to be > enabled if needed. > > Signed-off-by: James Clark > --- > drivers/hwtracing/coresight/coresight-etm-perf.c | 2 ++ > drivers/hwtracing/coresight/coresight-etm4x-core.c | 10 ++++++++++ > include/linux/coresight-pmu.h | 2 ++ > 3 files changed, 14 insertions(+) > > diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c > index c039b6ae206f..43bbd5dc3d3b 100644 > --- a/drivers/hwtracing/coresight/coresight-etm-perf.c > +++ b/drivers/hwtracing/coresight/coresight-etm-perf.c > @@ -52,6 +52,7 @@ static DEFINE_PER_CPU(struct coresight_device *, csdev_src); > * The PMU formats were orignally for ETMv3.5/PTM's ETMCR 'config'; > * now take them as general formats and apply on all ETMs. > */ > +PMU_FORMAT_ATTR(branch_broadcast, "config:"__stringify(ETM_OPT_BRANCH_BROADCAST)); > PMU_FORMAT_ATTR(cycacc, "config:" __stringify(ETM_OPT_CYCACC)); > /* contextid1 enables tracing CONTEXTIDR_EL1 for ETMv4 */ > PMU_FORMAT_ATTR(contextid1, "config:" __stringify(ETM_OPT_CTXTID)); > @@ -97,6 +98,7 @@ static struct attribute *etm_config_formats_attr[] = { > &format_attr_sinkid.attr, > &format_attr_preset.attr, > &format_attr_configid.attr, > + &format_attr_branch_broadcast.attr, Does it make sense to hide the option if the bb is not supported ? I guess it will be tricky as we don't track the common feature set. So, that said... > NULL, > }; > > diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c > index bf18128cf5de..04669ecc0efa 100644 > --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c > +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c > @@ -692,6 +692,16 @@ static int etm4_parse_event_config(struct coresight_device *csdev, > ret = cscfg_csdev_enable_active_config(csdev, cfg_hash, preset); > } > > + /* branch broadcast - enable if selected and supported */ > + if (attr->config & BIT(ETM_OPT_BRANCH_BROADCAST)) { > + if (!drvdata->trcbb) { > + ret = -EINVAL; Should we fail here ? We could simply ignore this and generate the trace normally. This would work on a big.LITTLE system with one set missing the branch broadcast, while the others support. Mike, Does this affect the trace decoding ? As such the OpenCSD should be able to decode the packets as they appear in the stream. Correct ? Suzuki > + goto out; > + } else { > + config->cfg |= BIT(ETM4_CFG_BIT_BB); > + } > + } > + > out: > return ret; > } > diff --git a/include/linux/coresight-pmu.h b/include/linux/coresight-pmu.h > index 4ac5c081af93..6c2fd6cc5a98 100644 > --- a/include/linux/coresight-pmu.h > +++ b/include/linux/coresight-pmu.h > @@ -18,6 +18,7 @@ > * ETMv3.5/PTM doesn't define ETMCR config bits with prefix "ETM3_" and > * directly use below macros as config bits. > */ > +#define ETM_OPT_BRANCH_BROADCAST 8 > #define ETM_OPT_CYCACC 12 > #define ETM_OPT_CTXTID 14 > #define ETM_OPT_CTXTID2 15 > @@ -25,6 +26,7 @@ > #define ETM_OPT_RETSTK 29 > > /* ETMv4 CONFIGR programming bits for the ETM OPTs */ > +#define ETM4_CFG_BIT_BB 3 > #define ETM4_CFG_BIT_CYCACC 4 > #define ETM4_CFG_BIT_CTXTID 6 > #define ETM4_CFG_BIT_VMID 7