linux-kernel - Re: [PATCH v2 6/8] ARCv2: perf: implement exclusion of event counting in user or kernel mode

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Date:	Wed, 19 Aug 2015 01:37:13 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Alexey Brodkin <Alexey.Brodkin@...opsys.com>
Cc:	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
	Vineet.Gupta1@...opsys.com, arc-linux-dev@...opsys.com,
	arnd@...db.de, Arnaldo Carvalho de Melo <acme@...nel.org>
Subject: Re: [PATCH v2 6/8] ARCv2: perf: implement exclusion of event
 counting in user or kernel mode

On Wed, Aug 05, 2015 at 06:13:32PM +0300, Alexey Brodkin wrote:
> +	hwc->config = 0;
> +
> +	if (is_isa_arcv2()) {
> +		/* "exclude user" means "count only kernel" */
> +		if (event->attr.exclude_user)
> +			hwc->config |= ARC_REG_PCT_CONFIG_KERN;
> +
> +		/* "exclude kernel" means "count only user" */
> +		if (event->attr.exclude_kernel)
> +			hwc->config |= ARC_REG_PCT_CONFIG_USER;
> +	}
> +
>  	switch (event->attr.type) {
>  	case PERF_TYPE_HARDWARE:
>  		if (event->attr.config >= PERF_COUNT_HW_MAX)
>  			return -ENOENT;
>  		if (arc_pmu->ev_hw_idx[event->attr.config] < 0)
>  			return -ENOENT;
> -		hwc->config = arc_pmu->ev_hw_idx[event->attr.config];
> +		hwc->config |= arc_pmu->ev_hw_idx[event->attr.config];

So I would still very much like perf_event_attr::config to reflect the
value you'll program into hardware.

If you want to do that weird 4 character lookup thing, use a special
hardware event (possibly 0 if that is not a valid value), and stuff the
4 chars in ::config1
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