Messages in this thread | | | From | Mike Leach <> | Date | Mon, 11 Jan 2021 16:22:39 +0000 | Subject | Re: [PATCH v1 1/7] coresight: etm-perf: Add support for PID tracing for kernel at EL2 |
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Hi Leo,
On Sat, 9 Jan 2021 at 07:44, Leo Yan <leo.yan@linaro.org> wrote: > > From: Suzuki K Poulose <suzuki.poulose@arm.com> > > 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 CONTEXTIDR_EL1. 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 <mathieu.poirier@linaro.org> > Cc: Al Grant <al.grant@arm.com> > Cc: Mike Leach <mike.leach@linaro.org> > Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com> > Signed-off-by: Leo Yan <leo.yan@linaro.org> > --- > 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 b20b6ff17cf6..8b7c7a8b2874 100644 > --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c > +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c > @@ -477,6 +477,15 @@ 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); > + } > + > /* 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
Minor issue here - ETMv3.x / PTM cannot trace CXTID in VMID so this may better be named ETM4_OPT_CTXTID_IN_VMID, rather than be grouped with the ETM3.5 options?
Regards
Mike
> +#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) > { > -- > 2.25.1 >
-- Mike Leach Principal Engineer, ARM Ltd. Manchester Design Centre. UK
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