linux-kernel - Re: [PATCH v16 31/34] fs/resctrl: Disable BMEC event configuration when mbm

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Message-ID: <46e6c50e-ab7d-49c0-b06f-aec51558af70@intel.com>
Date: Wed, 30 Jul 2025 13:11:03 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: Babu Moger <babu.moger@....com>, <corbet@....net>, <tony.luck@...el.com>,
	<james.morse@....com>, <tglx@...utronix.de>, <mingo@...hat.com>,
	<bp@...en8.de>, <dave.hansen@...ux.intel.com>
CC: <Dave.Martin@....com>, <x86@...nel.org>, <hpa@...or.com>,
	<akpm@...ux-foundation.org>, <paulmck@...nel.org>, <rostedt@...dmis.org>,
	<Neeraj.Upadhyay@....com>, <david@...hat.com>, <arnd@...db.de>,
	<fvdl@...gle.com>, <seanjc@...gle.com>, <jpoimboe@...nel.org>,
	<pawan.kumar.gupta@...ux.intel.com>, <xin@...or.com>,
	<manali.shukla@....com>, <tao1.su@...ux.intel.com>, <sohil.mehta@...el.com>,
	<kai.huang@...el.com>, <xiaoyao.li@...el.com>, <peterz@...radead.org>,
	<xin3.li@...el.com>, <kan.liang@...ux.intel.com>,
	<mario.limonciello@....com>, <thomas.lendacky@....com>, <perry.yuan@....com>,
	<gautham.shenoy@....com>, <chang.seok.bae@...el.com>,
	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<peternewman@...gle.com>, <eranian@...gle.com>
Subject: Re: [PATCH v16 31/34] fs/resctrl: Disable BMEC event configuration
 when mbm_event mode is enabled

Hi Babu,

On 7/25/25 11:29 AM, Babu Moger wrote:
> @@ -1799,6 +1800,41 @@ static ssize_t mbm_local_bytes_config_write(struct kernfs_open_file *of,
>  	return ret ?: nbytes;
>  }
>  
> +/*
> + * resctrl_bmec_files_show() — Controls the visibility of BMEC-related resctrl
> + * files. When @show is true, the files are displayed; when false, the files
> + * are hidden.
> + * Don't treat kernfs_find_and_get failure as an error, since this function may
> + * be called regardless of whether BMEC is supported or the event is enabled.
> + */
> +static void resctrl_bmec_files_show(struct rdt_resource *r, struct kernfs_node *l3_mon_kn,
> +				    bool show)
> +{
> +	struct kernfs_node *kn_config;
> +	char name[32];
> +
> +	if (!l3_mon_kn) {
> +		sprintf(name, "%s_MON", r->name);
> +		l3_mon_kn = kernfs_find_and_get(kn_info, name);
> +		if (!l3_mon_kn)
> +			return;
> +	}
> +
> +	kn_config = kernfs_find_and_get(l3_mon_kn, "mbm_total_bytes_config");
> +	if (kn_config) {
> +		kernfs_show(kn_config, show);
> +		kernfs_put(kn_config);
> +	}
> +
> +	kn_config = kernfs_find_and_get(l3_mon_kn, "mbm_local_bytes_config");
> +	if (kn_config) {
> +		kernfs_show(kn_config, show);
> +		kernfs_put(kn_config);
> +	}
> +
> +	kernfs_put(l3_mon_kn);

Looks like this will drop an extra reference if l3_mon_kn was provided as parameter.

Reinette