On 3/4/21 2:19 PM, Mike Leach wrote:

Hi Suzuki,

On Thu, 4 Mar 2021 at 12:13, Suzuki K Poulose [off-list ref] wrote:

quoted

On 1/28/21 5:09 PM, Mike Leach wrote:

quoted

Loaded coresight configurations are registered in the cs_etm\cs_config sub
directory. This extends the etm-perf code to handle these registrations,
and the cs_syscfg driver to perform the registration on load.

Signed-off-by: Mike Leach <redacted>
---
   .../hwtracing/coresight/coresight-config.h    |   5 +-
   .../hwtracing/coresight/coresight-etm-perf.c  | 164 +++++++++++++++---
   .../hwtracing/coresight/coresight-etm-perf.h  |   8 +
   .../hwtracing/coresight/coresight-syscfg.c    |  13 +-
   4 files changed, 166 insertions(+), 24 deletions(-)

quoted

quoted

+static ssize_t etm_perf_cscfg_event_show(struct device *dev,
+                                      struct device_attribute *dattr,
+                                      char *buf)
+{
+     struct dev_ext_attribute *ea;
+
+     ea = container_of(dattr, struct dev_ext_attribute, attr);
+     return scnprintf(buf, PAGE_SIZE, "%s\n", (const char *)(ea->var));
+}

"configid=0x%lx", (unsigned long)ea->var ?

ea->var _is_ "configid=0x%lx" due to the way perf handles the events
sub-dir entries.

This must be combined with the suggestion below.

quoted

quoted

+
+static int etm_perf_add_cscfg_event(struct device *dev, struct cscfg_config_desc *cs_cfg)
+{
+     struct dev_ext_attribute *ea;
+     unsigned long hash;
+     int ret;
+     struct device *pmu_dev = etm_pmu.dev;
+
+     ea = devm_kzalloc(dev, sizeof(*ea), GFP_KERNEL);
+     if (!ea)
+             return -ENOMEM;
+
+     hash = (unsigned long)cs_cfg->id_ea->var;
+
+     sysfs_attr_init(&ea->attr.attr);
+     ea->attr.attr.name = devm_kstrdup(dev, cs_cfg->name, GFP_KERNEL);
+     if (!ea->attr.attr.name)
+             return -ENOMEM;
+
+     /*
+      * attribute value is "configid=<hash>".
+      * this will be what perf evaluates when the config name is used
+      * on the command line.
+      */
+     ea->var = devm_kzalloc(dev, CSCFG_EVENT_STR_SIZE, GFP_KERNEL);
+     if (!ea->var)
+             return -ENOMEM;

Could we drop this string and use the "hash" instead ?

No. My understanding is that we have added an events directory to
cs_etm, and add the configurations in there:-

cs_etm/events/autofdo

Now the contents of autofdo are "configid=0x<hash-value>" - where
hash-value is the hash of "autofdo".

On the perf command line:-

perf record -e cs_etm/autofdo/ .....

will result in perf parsing autofdo, looking in the events dir for
cs_etm, seeing the configid=-string, and parsing that to assign to
configid attribute - which we have allocated to config2:63:32 - this
will then appear as a value in the perf_event and we can load the
configuration when starting up the event on the ETM etc.

Sorry, I was not explicit in my comments. You could drop the string and
have ea->var = hash. And the _show() could simply do

"configid=0x%lx" , hash

as mentioned above.

That would avoid another string allocation, with the same interface.

Suzuki