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

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Date:   Thu, 30 Mar 2017 11:46:08 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Anurup M <anurupvasu@...il.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 Thu, Mar 30, 2017 at 03:18:44PM +0530, Anurup M wrote:
> 
> 
> On Tuesday 21 March 2017 10:22 PM, Mark Rutland wrote:
> >+static int hisi_hw_perf_event_init(struct perf_event *event)
> >>+{
> >>+	struct hw_perf_event *hwc = &event->hw;
> >>+	struct hisi_pmu *hisi_pmu = to_hisi_pmu(event->pmu);
> >>+	struct device *dev = hisi_pmu->dev;
> >>+
> >>>+	/*
> >>>+	 * 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.

Thanks,
Mark.