linux-kernel - Re: [PATCH v6 07/11] drivers: perf: hisi: Add support for Hisilicon SoC event counters

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Date:   Fri, 31 Mar 2017 20:34:58 +0530
From:   Anurup M <anurupvasu@...il.com>
To:     Mark Rutland <mark.rutland@....com>
Cc:     will.deacon@....com, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, anurup.m@...wei.com,
        zhangshaokun@...ilicon.com, tanxiaojun@...wei.com,
        xuwei5@...ilicon.com, sanil.kumar@...ilicon.com,
        john.garry@...wei.com, gabriele.paoloni@...wei.com,
        shiju.jose@...wei.com, huangdaode@...ilicon.com,
        linuxarm@...wei.com, dikshit.n@...wei.com, shyju.pv@...wei.com
Subject: Re: [PATCH v6 07/11] drivers: perf: hisi: Add support for Hisilicon
 SoC event counters



On Friday 31 March 2017 07:53 PM, Mark Rutland wrote:
> On Fri, Mar 31, 2017 at 07:43:20PM +0530, Anurup M wrote:
>> On Thursday 30 March 2017 04:16 PM, Mark Rutland wrote:
>>>>>>> +	/*
>>>>>>>>>>> +	 * We must NOT create groups containing mixed PMUs, although
>>>>>>>>>>> +	 * software events are acceptable
>>>>>>>>>>> +	 */
>>>>>>>>>>> +	if (event->group_leader->pmu != event->pmu &&
>>>>>>>>>>> +	    !is_software_event(event->group_leader))
>>>>>>>>>>> +		return -EINVAL;
>>>>>>>>>>> +
>>>>>>>>>>> +	list_for_each_entry(sibling, &event->group_leader->sibling_list,
>>>>>>>>>>> +			    group_entry)
>>>>>>>>>>> +		if (sibling->pmu != event->pmu && !is_software_event(sibling))
>>>>>>>>>>> +			return -EINVAL;
>>>>>>> Please also check the number of counters.
>>>>> Sorry, I could not follow this comment correctly. Could you please explain ?
>>>>> I check the available counters and update used mask in pmu_add -->
>>>>> get_event_index
>>> What I meant was that here we should ensure that a group does not
>>> contain more events than can fit into counters.
>>>
>>> For example, if the HW had two counters, we should reject any group with
>>> more than two events. Such groups can never be scheduled, and make no
>>> sense.
>> I have referred drivers/bus/arm-cci.c and could find validate_group
>> and validate_event functions,
>> which create a fake_pmu to check the available counters for the
>> events in the group.
>> Is that the same way which is expected here? Please comment.
> Something like that.
>
> I think it's simplest to have a validate_group() function, which counts
> the number of counters used. See my suggestion in [1].

This looks simpler. Thanks for the suggestion.

~Anurup

> Thanks,
> Mark.
>
> [1] https://lkml.kernel.org/r/20170331135955.GB6488@leverpostej