linux-kernel - Re: [PATCH 14/21] x86/intel_rdt/cqm: Add mon

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Date:   Tue, 11 Jul 2017 14:17:47 -0700 (PDT)
From:   Shivappa Vikas <vikas.shivappa@...el.com>
To:     Thomas Gleixner <tglx@...utronix.de>
cc:     Shivappa Vikas <vikas.shivappa@...el.com>,
        Vikas Shivappa <vikas.shivappa@...ux.intel.com>,
        x86@...nel.org, linux-kernel@...r.kernel.org, hpa@...or.com,
        peterz@...radead.org, ravi.v.shankar@...el.com,
        tony.luck@...el.com, fenghua.yu@...el.com, andi.kleen@...el.com
Subject: Re: [PATCH 14/21] x86/intel_rdt/cqm: Add mon_data



On Thu, 6 Jul 2017, Thomas Gleixner wrote:

> On Thu, 6 Jul 2017, Shivappa Vikas wrote:
>> On Sun, 2 Jul 2017, Thomas Gleixner wrote:
>>>> +static bool __mon_event_count(u32 rmid, struct rmid_read *rr)
>>>> +{
>>>> +	u64 tval;
>>>> +
>>>> +	tval = __rmid_read(rmid, rr->evtid);
>>>> +	if (tval & (RMID_VAL_ERROR | RMID_VAL_UNAVAIL)) {
>>>> +		rr->val = tval;
>>>> +		return false;
>>>> +	}
>>>> +	switch (rr->evtid) {
>>>> +	case QOS_L3_OCCUP_EVENT_ID:
>>>> +		rr->val += tval;
>>>> +		return true;
>>>> +	default:
>>>> +		return false;
>>>
>>> I have no idea what that return code means.
>>
>> false for the invalid event id and all errors for __rmid_read. (IOW all errors
>> for __mon_event-read)
>
> Sure, but why bool? What's wrong with proper error return codes, so issues
> can be distinguished and potentially propagated in the callchain?

Ok, The error is propagated wih the rr->val actually. is this better?

Hardware throws the RMID_VAL_ERROR (bit 63) when an invalid RMID or 
event is written to event select - this case seems similar.

 	default:
 		rr->val = RMID_VAL_ERROR;
 		return -EINVAL;
 	}

Thanks,
Vikas

>
> Thanks,
>
> 	tglx
>
>
>
>
>