[PATCH v1 1/7] coresight: etm-perf: Add support for PID tracing for kernel at EL2

Leo Yan
2021-01-09T07:45:50Z

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
+#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