Le 11/02/2018 à 18:10, Vaibhav Jain a écrit :
Thanks for reviewing the patch Christophe,

christophe lombard <clomb...@linux.vnet.ibm.com> writes:
+bool cxl_enable_psltrace = true;
+module_param_named(enable_psltrace, cxl_enable_psltrace, bool, 0600);
+MODULE_PARM_DESC(enable_psltrace, "Set PSL traces on probe. default: on");
I am not too agree to add a new parameter. This can cause doubts.
PSL team has confirmed that enabling traces has no impact.
Do you see any reason to disable the traces ?

Traces on PSL follow a 'set and fetch' model. So once the trace buffer for
a specific array is full it will stop and switch to 'FIN' state and at
that point we need to fetch the trace-data and reinit the array to
re-arm it.

If the PSL trace arrays don't wrap, is there anything to gain by enabling tracing by default instead of letting the developer handle it through sysfs? I was under the (now wrong) impression that the PSL would wrap. I'm not a big fan of the module parameter. It seems we're giving a second way of activating traces on top of sysfs, more cumbersome and limited.


There might be some circumstances where this model may lead to confusion
specifically when AFU developers assume that the trace arrays are
already armed and dont re-arm it causing miss of trace data.

So this module param is a compromise to keep the old behaviour of traces
array intact where in the arming/disarming of the trace arrays is
controlled completely by userspace tooling and not by cxl.

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