Date: Fri, 31 Mar 2017 15:23:52 +0100
From: Mark Rutland <mark.rutland@arm.com>
To: Anurup M <anurupvasu@gmail.com>
Cc: will.deacon@arm.com, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, anurup.m@huawei.com,
        zhangshaokun@hisilicon.com, tanxiaojun@huawei.com,
        xuwei5@hisilicon.com, sanil.kumar@hisilicon.com, john.garry@huawei.com,
        gabriele.paoloni@huawei.com, shiju.jose@huawei.com,
        huangdaode@hisilicon.com, linuxarm@huawei.com, dikshit.n@huawei.com,
        shyju.pv@huawei.com
Subject: Re: [PATCH v6 07/11] drivers: perf: hisi: Add support for Hisilicon
 SoC event counters
Message-ID: <20170331142351.GC6488@leverpostej>
References: <1489127311-112778-1-git-send-email-anurup.m@huawei.com>
 <20170321165252.GA29116@leverpostej>
 <58DCD47C.2010501@gmail.com>
 <20170330104607.GC16211@leverpostej>
 <58DE6400.8030900@gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <58DE6400.8030900@gmail.com>
User-Agent: Mutt/1.5.21 (2010-09-15)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1656
Lines: 41

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].

Thanks,
Mark.

[1] https://lkml.kernel.org/r/20170331135955.GB6488@leverpostej