linux-kernel - Re: [PATCH v8 12/25] x86/resctrl: Remove MSR reading of event configuration value

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Message-ID: <dd53ed4f-d1c3-4b1c-9f4c-1852a64e9d87@intel.com>
Date: Tue, 15 Oct 2024 20:16:01 -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 v8 12/25] x86/resctrl: Remove MSR reading of event
 configuration value

Hi Babu,

On 10/9/24 10:39 AM, Babu Moger wrote:
> The event configuration is domain specific and initialized during domain
> initialization. The values are stored in struct rdt_hw_mon_domain.
> 
> It is not required to read the configuration register every time user asks
> for it. Use the value stored in struct rdt_hw_mon_domain instead.
> 
> Introduce resctrl_arch_mon_event_config_get() and
> resctrl_arch_mon_event_config_set() to get/set architecture domain specific
> mbm_total_cfg/mbm_local_cfg values.
> 
> Signed-off-by: Babu Moger <babu.moger@....com>
> ---
...


> +void resctrl_arch_mon_event_config_set(void *info)
> +{
> +	struct mon_config_info *mon_info = info;
> +	struct rdt_hw_mon_domain *hw_dom;
> +	unsigned int index;
> +
> +	index = mon_event_config_index_get(mon_info->evtid);
> +	if (index == INVALID_CONFIG_INDEX)
> +		return;
> +
> +	wrmsr(MSR_IA32_EVT_CFG_BASE + index, mon_info->mon_config, 0);
> +
> +	hw_dom = resctrl_to_arch_mon_dom(mon_info->d);
> +
> +	switch (mon_info->evtid) {
> +	case QOS_L3_OCCUP_EVENT_ID:
> +		break;

This check does no harm but I do not think it is necessary since earlier
mon_event_config_index_get() would return INVALID_CONFIG_INDEX if the
evtid is QOS_L3_OCCUP_EVENT_ID.

> +	case QOS_L3_MBM_TOTAL_EVENT_ID:
> +		hw_dom->mbm_total_cfg = mon_info->mon_config;
> +		break;
> +	case QOS_L3_MBM_LOCAL_EVENT_ID:
> +		hw_dom->mbm_local_cfg =  mon_info->mon_config;

nit: unnecessary space

> +		break;
> +	}
> +}
> +

Reinette