linux-kernel - Re: [PATCH v11 10/23] x86/resctrl: Remove MSR reading of event configuration value

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Message-ID: <ead5a097-44f7-4eaa-8e98-08450b4d51f6@zytor.com>
Date: Wed, 5 Feb 2025 22:24:58 -0800
From: Xin Li <xin@...or.com>
To: Babu Moger <babu.moger@....com>, corbet@....net, reinette.chatre@...el.com,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, tony.luck@...el.com,
        peternewman@...gle.com
Cc: fenghua.yu@...el.com, x86@...nel.org, hpa@...or.com, paulmck@...nel.org,
        akpm@...ux-foundation.org, thuth@...hat.com, rostedt@...dmis.org,
        xiongwei.song@...driver.com, pawan.kumar.gupta@...ux.intel.com,
        daniel.sneddon@...ux.intel.com, jpoimboe@...nel.org,
        perry.yuan@....com, sandipan.das@....com, kai.huang@...el.com,
        xiaoyao.li@...el.com, seanjc@...gle.com, xin3.li@...el.com,
        andrew.cooper3@...rix.com, ebiggers@...gle.com,
        mario.limonciello@....com, james.morse@....com,
        tan.shaopeng@...itsu.com, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, maciej.wieczor-retman@...el.com,
        eranian@...gle.com
Subject: Re: [PATCH v11 10/23] x86/resctrl: Remove MSR reading of event
 configuration value

On 1/22/2025 12:20 PM, Babu Moger wrote:
> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
> index 8917c7261680..6fe9e610e9a0 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -1324,3 +1324,49 @@ int resctrl_arch_mbm_cntr_assign_set(struct rdt_resource *r, bool enable)
>   
>   	return 0;
>   }
> +
> +u32 resctrl_arch_mon_event_config_get(struct rdt_mon_domain *d,
> +				      enum resctrl_event_id eventid)
> +{
> +	struct rdt_hw_mon_domain *hw_dom = resctrl_to_arch_mon_dom(d);
> +
> +	switch (eventid) {
> +	case QOS_L3_OCCUP_EVENT_ID:
> +		break;
> +	case QOS_L3_MBM_TOTAL_EVENT_ID:
> +		return hw_dom->mbm_total_cfg;
> +	case QOS_L3_MBM_LOCAL_EVENT_ID:
> +		return hw_dom->mbm_local_cfg;
> +	}
> +
> +	/* Never expect to get here */
> +	WARN_ON_ONCE(1);
> +
> +	return INVALID_CONFIG_VALUE;
> +}
> +
> +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);

This is the existing code, however it would be better to use wrmsrl()
when the higher 32-bit are all 0s:

	wrmsrl(MSR_IA32_EVT_CFG_BASE + index, mon_info->mon_config);

Thanks!
     Xin