linux-kernel - Re: [PATCH V4 4/7] perf/x86/intel: Support LBR event logging

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Date:   Thu, 19 Oct 2023 11:26:43 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     kan.liang@...ux.intel.com
Cc:     mingo@...hat.com, acme@...nel.org, linux-kernel@...r.kernel.org,
        mark.rutland@....com, alexander.shishkin@...ux.intel.com,
        jolsa@...nel.org, namhyung@...nel.org, irogers@...gle.com,
        adrian.hunter@...el.com, ak@...ux.intel.com, eranian@...gle.com,
        alexey.v.bayduraev@...ux.intel.com, tinghao.zhang@...el.com
Subject: Re: [PATCH V4 4/7] perf/x86/intel: Support LBR event logging

On Wed, Oct 04, 2023 at 11:40:41AM -0700, kan.liang@...ux.intel.com wrote:

> +
>  static struct attribute *lbr_attrs[] = {
>  	&dev_attr_branches.attr,
> +	&dev_attr_branch_counter_nr.attr,
> +	&dev_attr_branch_counter_width.attr,
>  	NULL
>  };
>  
> @@ -5590,7 +5665,11 @@ mem_is_visible(struct kobject *kobj, struct attribute *attr, int i)
>  static umode_t
>  lbr_is_visible(struct kobject *kobj, struct attribute *attr, int i)
>  {
> -	return x86_pmu.lbr_nr ? attr->mode : 0;
> +	/* branches */
> +	if (i == 0)
> +		return x86_pmu.lbr_nr ? attr->mode : 0;
> +
> +	return (x86_pmu.flags & PMU_FL_LBR_EVENT) ? attr->mode : 0;
>  }

As in the patch this is fairly readable, but I just checked and in the
code lbr_attrs and lbr_is_visible() are rather far away from one another
which makes the whole i thing hard to interpret.

Should we re-organize that a little?