linux-kernel - Re: [PATCH v6 19/22] x86/resctrl: Introduce the interface to switch between monitor modes

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Message-ID: <ef586a11-5d8f-434f-962c-6893ae4668de@intel.com>
Date: Fri, 16 Aug 2024 14:42:52 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: Babu Moger <babu.moger@....com>, <corbet@....net>, <fenghua.yu@...el.com>,
	<tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
	<dave.hansen@...ux.intel.com>
CC: <x86@...nel.org>, <hpa@...or.com>, <paulmck@...nel.org>,
	<rdunlap@...radead.org>, <tj@...nel.org>, <peterz@...radead.org>,
	<yanjiewtw@...il.com>, <kim.phillips@....com>, <lukas.bulwahn@...il.com>,
	<seanjc@...gle.com>, <jmattson@...gle.com>, <leitao@...ian.org>,
	<jpoimboe@...nel.org>, <rick.p.edgecombe@...el.com>,
	<kirill.shutemov@...ux.intel.com>, <jithu.joseph@...el.com>,
	<kai.huang@...el.com>, <kan.liang@...ux.intel.com>,
	<daniel.sneddon@...ux.intel.com>, <pbonzini@...hat.com>,
	<sandipan.das@....com>, <ilpo.jarvinen@...ux.intel.com>,
	<peternewman@...gle.com>, <maciej.wieczor-retman@...el.com>,
	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<eranian@...gle.com>, <james.morse@....com>
Subject: Re: [PATCH v6 19/22] x86/resctrl: Introduce the interface to switch
 between monitor modes

Hi Babu,

On 8/6/24 3:00 PM, Babu Moger wrote:
> +static ssize_t rdtgroup_mbm_mode_write(struct kernfs_open_file *of,
> +				       char *buf, size_t nbytes,
> +				       loff_t off)
> +{
> +	int mbm_cntr_assign = resctrl_arch_get_abmc_enabled();

This needs to be protected by the mutex.

> +	struct rdt_resource *r = of->kn->parent->priv;
> +	int ret = 0;
> +
> +	/* Valid input requires a trailing newline */
> +	if (nbytes == 0 || buf[nbytes - 1] != '\n')
> +		return -EINVAL;
> +
> +	buf[nbytes - 1] = '\0';
> +
> +	cpus_read_lock();
> +	mutex_lock(&rdtgroup_mutex);
> +
> +	rdt_last_cmd_clear();
> +
> +	if (!strcmp(buf, "legacy")) {
> +		if (mbm_cntr_assign)
> +			resctrl_arch_mbm_cntr_assign_disable();
> +	} else if (!strcmp(buf, "mbm_cntr_assign")) {
> +		if (!mbm_cntr_assign) {
> +			rdtgroup_mbm_cntr_reset(r);
> +			ret = resctrl_arch_mbm_cntr_assign_enable();
> +		}
> +	} else {
> +		ret = -EINVAL;
> +	}
> +
> +	mutex_unlock(&rdtgroup_mutex);
> +	cpus_read_unlock();
> +
> +	return ret ?: nbytes;
> +}
> +

Reinette