Re: [PATCH 2/3] cxl: Introduce module parameter 'enable_psltrace'

Le 11/02/2018 à 18:10, Vaibhav Jain a écrit :

Thanks for reviewing the patch Christophe,

christophe lombard [off-list ref] writes:

quoted

quoted

+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.

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.

and about P8 ? This new parameter is only useful for P9. It will be 
confusing.