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Thu, 12 Nov 2020 02:27:22 -0800 (PST) Date: Thu, 12 Nov 2020 18:27:17 +0800 From: Leo Yan To: Suzuki K Poulose Subject: Re: [PATCH 1/3] coresight: etm-perf: Add support for PID tracing for kernel at EL2 Message-ID: <20201112102717.GC17274@leoy-ThinkPad-X240s> References: <20201110183313.1823760-1-suzuki.poulose@arm.com> <20201110183313.1823760-2-suzuki.poulose@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20201110183313.1823760-2-suzuki.poulose@arm.com> User-Agent: Mutt/1.9.4 (2018-02-28) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201112_052726_054608_A418EC07 X-CRM114-Status: GOOD ( 34.18 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: al.grant@arm.com, mathieu.poirier@linaro.org, anshuman.khandual@arm.com, coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org, mike.leach@linaro.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Nov 10, 2020 at 06:33:11PM +0000, Suzuki Kuruppassery Poulose wrote: > When the kernel is running at EL2, the PID is stored in CONTEXTIDR_EL2. > So, tracing CONTEXTIDR_EL1 doesn't give us the pid of the process. > Thus we should trace the VMID with VMIDOPT set to trace > CONTEXTIDR_EL2 instead of VMID. Given that we have an existing > config option "contextid" and this will be useful for tracing > virtual machines (when we get to support virtualization). So instead, > this patch adds a new option, contextid_in_vmid as a separate config. > Thus on an EL2 kernel, we will have two options available for > the perf tool. However, to make it easier for the user to > do pid tracing, we add a new format which will default to > "contextid" (on EL1 kernel) or "contextid_in_vmid" (on EL2 > kernel). So that the user doesn't have to bother which EL the > kernel is running. > > i.e, perf record -e cs_etm/pid/u -- > > will always do the "pid" tracing, independent of the kernel EL. > > Also, the perf tool will be updated to automatically select > "pid" config instead of the "contextid" for system wide/CPU wide > mode. > > Cc: Mathieu Poirier > Cc: Al Grant > Cc: Mike Leach > Cc: Leo Yan > Signed-off-by: Suzuki K Poulose > --- > drivers/hwtracing/coresight/coresight-etm-perf.c | 14 ++++++++++++++ > drivers/hwtracing/coresight/coresight-etm4x-core.c | 9 +++++++++ > include/linux/coresight-pmu.h | 11 +++++++---- > 3 files changed, 30 insertions(+), 4 deletions(-) > > diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c > index bdc34ca449f7..f763def145e4 100644 > --- a/drivers/hwtracing/coresight/coresight-etm-perf.c > +++ b/drivers/hwtracing/coresight/coresight-etm-perf.c > @@ -30,14 +30,28 @@ static DEFINE_PER_CPU(struct coresight_device *, csdev_src); > /* ETMv3.5/PTM's ETMCR is 'config' */ > PMU_FORMAT_ATTR(cycacc, "config:" __stringify(ETM_OPT_CYCACC)); > PMU_FORMAT_ATTR(contextid, "config:" __stringify(ETM_OPT_CTXTID)); > +PMU_FORMAT_ATTR(contextid_in_vmid, "config:" __stringify(ETM_OPT_CTXTID_IN_VMID)); > PMU_FORMAT_ATTR(timestamp, "config:" __stringify(ETM_OPT_TS)); > PMU_FORMAT_ATTR(retstack, "config:" __stringify(ETM_OPT_RETSTK)); > /* Sink ID - same for all ETMs */ > PMU_FORMAT_ATTR(sinkid, "config2:0-31"); > > +static ssize_t format_attr_pid_show(struct device *dev, > + struct device_attribute *attr, > + char *page) > +{ > + int pid_fmt = is_kernel_in_hyp_mode() ? ETM_OPT_CTXTID_IN_VMID : ETM_OPT_CTXTID; > + > + return sprintf(page, "config:%d\n", pid_fmt); > +} > + > +struct device_attribute format_attr_pid = __ATTR(pid, 0444, format_attr_pid_show, NULL); > + > static struct attribute *etm_config_formats_attr[] = { > &format_attr_cycacc.attr, > &format_attr_contextid.attr, > + &format_attr_contextid_in_vmid.attr, > + &format_attr_pid.attr, > &format_attr_timestamp.attr, > &format_attr_retstack.attr, > &format_attr_sinkid.attr, > diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c > index d78a37b6592c..8cb2cb1febce 100644 > --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c > +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c > @@ -382,6 +382,15 @@ static int etm4_parse_event_config(struct etmv4_drvdata *drvdata, > /* bit[6], Context ID tracing bit */ > config->cfg |= BIT(ETM4_CFG_BIT_CTXTID); > > + /* Do not enable VMID tracing if we are not running in EL2 */ > + if (attr->config & BIT(ETM_OPT_CTXTID_IN_VMID)) { > + if (!is_kernel_in_hyp_mode()) { > + ret = -EINVAL; > + goto out; > + } > + config->cfg |= BIT(ETM4_CFG_BIT_VMID) | BIT(ETM4_CFG_BIT_VMID_OPT); > + } > + Nitpick: should the driver need to check the kernel running mode for the config ETM_OPT_CTXTID? I.e. if the BIT(ETM_OPT_CTXTID) is set in "attr->config", does it mean the kernel should run in EL1 mode? Just curious, does there have a scenario that we need to set BIT ETM4_CFG_BIT_VMID but the bit ETM4_CFG_BIT_VMID_OPT is cleared? I think a bit for this, but cannot find a situation for tracing context ID based on VTTBR_EL2.VMID. So this might be not a question for us. Thanks, Leo > /* return stack - enable if selected and supported */ > if ((attr->config & BIT(ETM_OPT_RETSTK)) && drvdata->retstack) > /* bit[12], Return stack enable bit */ > diff --git a/include/linux/coresight-pmu.h b/include/linux/coresight-pmu.h > index b0e35eec6499..927c6285ce5d 100644 > --- a/include/linux/coresight-pmu.h > +++ b/include/linux/coresight-pmu.h > @@ -11,16 +11,19 @@ > #define CORESIGHT_ETM_PMU_SEED 0x10 > > /* ETMv3.5/PTM's ETMCR config bit */ > -#define ETM_OPT_CYCACC 12 > -#define ETM_OPT_CTXTID 14 > -#define ETM_OPT_TS 28 > -#define ETM_OPT_RETSTK 29 > +#define ETM_OPT_CYCACC 12 > +#define ETM_OPT_CTXTID 14 > +#define ETM_OPT_CTXTID_IN_VMID 15 > +#define ETM_OPT_TS 28 > +#define ETM_OPT_RETSTK 29 > > /* ETMv4 CONFIGR programming bits for the ETM OPTs */ > #define ETM4_CFG_BIT_CYCACC 4 > #define ETM4_CFG_BIT_CTXTID 6 > +#define ETM4_CFG_BIT_VMID 7 > #define ETM4_CFG_BIT_TS 11 > #define ETM4_CFG_BIT_RETSTK 12 > +#define ETM4_CFG_BIT_VMID_OPT 15 > > static inline int coresight_get_trace_id(int cpu) > { > -- > 2.24.1 > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel